Supporting Builtin Float?

[mtoohey31]

As of a while ago, Nix has builtin floats. Would you be open to a PR that refactors everything that uses this custom float type to use the builtin float type?

[mtoohey31]

Actually, I suppose for backwards compatability we should refactor so that the custom float type accepts builtin float, as well as all the types it currently accepts.

[beetcb]

Yeah, a little bit frustrating that the float(in mannul) is actually string. I think we can start with improving the documentation first @LnL7