Feature definitions simplified

The argument names and types are already included in the feature descriptor.
Therefore they have been dropped from the definition.

	modified:   ocaml/feature_table.ml
Added formal generic names to classes and the function 'type2string'

	modified:   ocaml/class_table.ml
	modified:   ocaml/class_table.mli
Completed the draft of the type checking algorithm

	modified:   ocaml/context.ml
	modified:   ocaml/feature_table.ml
	modified:   ocaml/feature_table.mli
	modified:   ocaml/typer.ml
The type checker with type inference is fully integrated

	modified:   library/kernel/boolean.e
	modified:   ocaml/class_table.ml
	modified:   ocaml/class_table.mli
	modified:   ocaml/context.ml
	modified:   ocaml/eiffelc.ml
	modified:   ocaml/feature_table.ml
	modified:   ocaml/feature_table.mli
	modified:   ocaml/prover.ml
	modified:   ocaml/signature.ml
	modified:   ocaml/typer.ml