PicoSAT integration:
	-fix known bug in getting the proof for PicoSat

LA:
    -get implied equalites:
     faster incremental implementation ?? (seems not any faster)
    -over-approx for the unsat core -> faster
    -use the arbitrary precision solver (when no more that experimental)

EUF:
	-improve the unsat core (over-approximation)

Nelson Oppen:

DL:
	-add difference logic


Delayed theory combination:
    -needed ?? (not really )

General:
    -multiple interpolant from one query (path): finish the code
    -cleanup the code
