Renamed Language.Salt.Core.ProofScript to Language.Salt.Core.Proofs.ProofScript
Renamed Language.Salt.Core.ProofScript to Language.Salt.Core.Proofs.ProofScript
Fixed ambigious symbol problem with Proof typeclass.
Added proof error message class.
Renamed Language.Salt.Core.PatternMatch to Language.Salt.Core.Patterns
Added module containing datatypes for proof states and proof goals
Added diagnostic messages for incomplete and complete proofs.