Removed an unneeded function

	modified:   ocaml/prover.ml
Reworked 'term_table.ml'

- Added comments to describe the datastructure and the algorithm
- Completed the functions for lambda abstractions
- Simplified the map for other variables

	modified:   ocaml/term_table.ml
Fix: 'Term.implication_chain' used correctly

The calculation of the backward rules in 'general_context.ml' was still
expecting the implication chain as calculated previously in 'feature_table.ml'
which calculated the chain in reverse order.

	modified:   ocaml/general_context.ml
Tried 'Term.implication_chain2', but does not yet work

Therefore reverted to the previous version and left usage of
'implication_chain2' in as commented code.

Removed 'makefile' because it is just a convenience file for the
time being.

	modified:   ocaml/general_context.ml
	deleted:    ocaml/makefile
	modified:   ocaml/prover.ml
	modified:   ocaml/term.ml