Merge quantifiers2-trunk:

Merge quantifiers2-trunk:
   - new syntax for rewrite rules
   - better rewrite rules theory
   - remove the rewriting with rewrite rules during ppRewrite temporarily
   - theory can define their own candidate generator
   - define a general candidate generator (inefficient ask to every theory)
   - split inst_match between the pattern matching used for quantifiers (inst_match.*) and
     the one used for rewrite rules (rr_inst_match.*):
      - the pattern matching is less exhaustive for quantifiers,
      - the one for rewrite rules can use efficient-e-matching.