TPTP: add parser for cnf and fof

TPTP: add parser for cnf and fof
 - include directive works
 - no keyword : 'fof', 'cnf', ... can be used for symbols name
 - real -> unsorted -> real (for the one that appear, so no bijection bitween real and unsorted)
 - same thing for string

But:
 - string not distinct by projection to real, not sure if the current state of string theory make them distinct
 - filtering in include is not done
 - the result is not printed in the TPTP way (currently SMT2 way)