Rename Transakcio to Til for a easier usage, also change til.TestContext
to til.Context, and til.NewTestContext to til.NewContext.

Transakcio:
- Transaction generation to fail when Transfer to an account that don't exist (not created yet)
- Add CreateAccountDepositCoordinator instruction feature
- Updated lang.go instruction type parser approach for more simplicity of code
- Remove `*testing.T` from transactions generation methods, use `log.Fatal` instead

Add transakcio set type definition, add set loading, move transakcio to
package, adapt branch to last master updates (fix compile due new common
types & git conflicts).
Update tests to pass the test, pending to adapt to new Transakcio
interface.