Add poseidon benchmark with 16 elements

* Switch to keccac256 implementation from golang.org/x/crypto instead of go-ethereum

* Extend poseidon to 16 inputs. Better initialization of Poseidon constants
* Update deps
* Fix linter warnings
* Test vectors for poseidon with 14 inputs

* implemented optimized poseidon

* added comment to poseidon hash function

* deleted poseidonslow

Update Poseidon last changes of the reference impl

Update Poseidon to last changes of the reference implementation from
26ddaa91db

Compatible with update at circomlib
(cf853c1cc9)

Update and add test for PackSignY & UnpackSignY

- Update PackSignY & UnpackSignY interface and description
- Add test for UnpackSignY & PackPoint

Abstract & expose CompressedPointToSignAndY

Add scanner/valuer interface to babyjub.PublicKeyComp

Upgrade linters

Update BabyJubJub EdDSA to last circomlib version

- Update BabyJubJub EdDSA signature to last circomlib version (Poseidon
usage)
- Remove panic on hash error inside verification, to avoid panic due
field overflow of BabyJubJub signature verification

Add scanner/valuer interface to babyjub.SignatureComp

- Add `add-2008-bbjlp` for point addition
- Add `goff` to BabyJubJub point addition

```
Benchmarks (On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM):

- Old (commit: e04ca5764a):
BenchmarkBabyjub/AddConst-8              1000000              1072 ns/op
BenchmarkBabyjub/AddRnd-8                  93417             12943 ns/op
BenchmarkBabyjub/MulRnd-8                    252           4797810 ns/op
BenchmarkBabyjub/Compress-8              7291580               166 ns/op
BenchmarkBabyjub/InCurve-8                611137              1999 ns/op
BenchmarkBabyjub/InSubGroup-8             615792              2021 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            126           9358542 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          124           9484005 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 126           9486484 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               126           9622807 ns/op

- With new point addition algorithm (commit: aab1a681dd4b00cab49f39f9e30d6f28034589c1):
BenchmarkBabyjub/AddConst-8              1356836               881 ns/op
BenchmarkBabyjub/AddRnd-8                 274112              4220 ns/op
BenchmarkBabyjub/MulRnd-8                    492           2474412 ns/op
BenchmarkBabyjub/Compress-8              6964855               197 ns/op
BenchmarkBabyjub/InCurve-8                608169              2008 ns/op
BenchmarkBabyjub/InSubGroup-8             618772              1954 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            238           4962397 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          235           5234883 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 240           5028720 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               243           5226654 ns/op

Point Addition: ~3x
Point scalar Mul: ~1.9x
Signature (poseidon): ~1.88x
Verification (poseidon): ~1.84x

- With new point addition algorithm & goff (current commit):
BenchmarkBabyjub/AddConst-8              3000531               400 ns/op
BenchmarkBabyjub/AddRnd-8                2770335               428 ns/op
BenchmarkBabyjub/MulRnd-8                   6636            175522 ns/op
BenchmarkBabyjub/Compress-8              7358768               180 ns/op
BenchmarkBabyjub/InCurve-8                539193              1950 ns/op
BenchmarkBabyjub/InSubGroup-8             601402              1958 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8           2940            409487 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8         2908            414407 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                2395            493165 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8              2491            494849 ns/op

Point Addition: ~9.86x
Point scalar Mul: ~14x
Signature (poseidon): ~10.2x
Verification (poseidon): ~10.56x

---

Total improvement (from old to current):
Point Addition: ~30.24x
Point scalar Mul: ~27.33x
Signature (poseidon): ~19.24x
Verification (poseidon): ~19.44x
```

```
Benchmarks (On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM):

- Old (commit: e04ca5764a):
BenchmarkBabyjub/AddConst-8              1000000              1072 ns/op
BenchmarkBabyjub/AddRnd-8                  93417             12943 ns/op
BenchmarkBabyjub/MulRnd-8                    252           4797810 ns/op
BenchmarkBabyjub/Compress-8              7291580               166 ns/op
BenchmarkBabyjub/InCurve-8                611137              1999 ns/op
BenchmarkBabyjub/InSubGroup-8             615792              2021 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            126           9358542 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          124           9484005 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 126           9486484 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               126           9622807 ns/op

- With new point addition algorithm (commit: aab1a681dd4b00cab49f39f9e30d6f28034589c1):
BenchmarkBabyjub/AddConst-8              1356836               881 ns/op
BenchmarkBabyjub/AddRnd-8                 274112              4220 ns/op
BenchmarkBabyjub/MulRnd-8                    492           2474412 ns/op
BenchmarkBabyjub/Compress-8              6964855               197 ns/op
BenchmarkBabyjub/InCurve-8                608169              2008 ns/op
BenchmarkBabyjub/InSubGroup-8             618772              1954 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            238           4962397 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          235           5234883 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 240           5028720 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               243           5226654 ns/op

Point Addition: ~3x
Point scalar Mul: ~1.9x
Signature (poseidon): ~1.88x
Verification (poseidon): ~1.84x

- With new point addition algorithm & goff (current commit):
BenchmarkBabyjub/AddConst-8              3000531               400 ns/op
BenchmarkBabyjub/AddRnd-8                2770335               428 ns/op
BenchmarkBabyjub/MulRnd-8                   6636            175522 ns/op
BenchmarkBabyjub/Compress-8              7358768               180 ns/op
BenchmarkBabyjub/InCurve-8                539193              1950 ns/op
BenchmarkBabyjub/InSubGroup-8             601402              1958 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8           2940            409487 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8         2908            414407 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                2395            493165 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8              2491            494849 ns/op

Point Addition: ~9.86x
Point scalar Mul: ~14x
Signature (poseidon): ~10.2x
Verification (poseidon): ~10.56x

---

Total improvement (from old to current):
Point Addition: ~30.24x
Point scalar Mul: ~27.33x
Signature (poseidon): ~19.24x
Verification (poseidon): ~19.44x
```

Add `add-2008-bbjlp` for point addition

Benchmarks (On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM):

```
- Old:
BenchmarkBabyjub/AddConst-8              1000000              1072 ns/op
BenchmarkBabyjub/AddRnd-8                  93417             12943 ns/op
BenchmarkBabyjub/MulRnd-8                    252           4797810 ns/op
BenchmarkBabyjub/Compress-8              7291580               166 ns/op
BenchmarkBabyjub/InCurve-8                611137              1999 ns/op
BenchmarkBabyjub/InSubGroup-8             615792              2021 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            126           9358542 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          124           9484005 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 126           9486484 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               126           9622807 ns/op

- With new point addition algorithm:
BenchmarkBabyjub/AddConst-8              1356836               881 ns/op
BenchmarkBabyjub/AddRnd-8                 274112              4220 ns/op
BenchmarkBabyjub/MulRnd-8                    492           2474412 ns/op
BenchmarkBabyjub/Compress-8              6964855               197 ns/op
BenchmarkBabyjub/InCurve-8                608169              2008 ns/op
BenchmarkBabyjub/InSubGroup-8             618772              1954 ns/op
BenchmarkBabyjubEddsa/SignMimc7-8            238           4962397 ns/op
BenchmarkBabyjubEddsa/VerifyMimc7-8          235           5234883 ns/op
BenchmarkBabyjubEddsa/SignPoseidon-8                 240           5028720 ns/op
BenchmarkBabyjubEddsa/VerifyPoseidon-8               243           5226654 ns/op
```

Point Addition: ~3x
Point scalar Mul: ~1.9x
Signature (poseidon): ~1.88x
Verification (poseidon): ~1.84x

Fix value sql interface

Add scanner/valuer interface to signature

Babyjubjub separate PointFromSignAndY from p.Decompress

Update Poseidon Hash function names, rm HashBytes

Since Poseidon Hash is used because of compatibility in zkSNARK circuits, due
circuit constraints number, the hash method of [T]*big.Int is the one directly
compatible with the circuits, is the method which have the `Hash` name on it.
The method that can take arbitrary length of []*big.Int putting them in chunks
of [T]*big.Int and iterating, is called `HashSlice`. The `HashBytes` has been
removed, as is a method that will not be used in zkSNARK circuits due high
constraints number.

For zkSNARK circuits, should be used `poseidon.Hash([poseidon.T]*big.Int)`.

Poseidon & MiMC7 HashBytes remove return of err

Expose SkToBigInt for usage from other packages & repos

Add utils.ElementArrayToBigIntArray

Add github actions and remove travis

Fix compat with 32 bit arch

Feature/mimc7 goff