Removed 'proof.ml' which is no longer necessary

	modified:   ocaml/context.ml
	deleted:    ocaml/proof.ml
Prepared coded for inheritance and modules

- Moved unification of type expressions to 'typer.ml'
- Fixed a bug in the unifier with formal generics

	modified:   library/kernel/any.e
	modified:   ocaml/context.ml
	modified:   ocaml/context.mli
	modified:   ocaml/signature.ml
	modified:   ocaml/term.ml
	modified:   ocaml/typer.ml