Co-authored-by: Sun <huachuang20@gmail.com>
Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

* impl sum for fpvar

* fmt

* grammar

* update the CHANGELOG

Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

This is related to a Zexe issue https://github.com/scipr-lab/zexe/issues/289

Basically, ToBitsGadget for FpVar may produce shorter output for a constant value, which is undesired for a few reasons.

Co-authored-by: Nicholas Ward <npward@berkeley.edu>

* `to_bits` -> `to_bits_le`
* `BitIterator` -> `BitIteratorLE` + `BitIteratorBE`
* `found_one`/`seen_one` -> `BitIteratorBE::without_leading_zeros`

Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

* adds alloc constant to AllocGadget

* fmt

* fmt

* more alloc constant impls

* fmt

* even more impls

* fixes type

* fixes alloc_constant in gm17

* uses alloc_constant from field gadget in group gadgets

* fmt

* handle most comments

* Add mnt6_753 curve
Generalize mnt6 curve model

* Add mnt4 curves

* Use resampled generators

* Calculate correct G2 cofactors

* Add fields to r1cs-std

* Add pairings

* Improve reusing of Fq/Fr among MNT curves

* Add instantiations of curves
Fix Fp6_2over3
Rebase code to current master

* Add test for recursive NIZK proof verification

* Address comments in PR

* Improve test case and port to GM17
Also fix a minor bug in to_field_vec

eliminate a few redundant references