Add a strategic evaluation systema based on Eelco Visser's article 'Strategic Pattern Matching'.
- the strategy file contains the type
- the strategies file contains the default strategies and string convertion

The strageies can be tested by modifying the one given to rec_rewrite until the parsing is implemented.

The next step is to implement the parsing part.
Add an optimisation to the rec strategy
Remove old strategies in rewriting
Merge branch 'master' of https://github.com/ptal/nominal-workbench

Conflicts:
	src/algorithms/rewriting.ml
	src/algorithms/rewriting.mli
	src/driver/eval.ml
	test/test.ml
Continue the merging, usable program with future work annoted.