fixed a typo in const.hs
o removed the excessive bool flag from ProofObligation and CheckSat (from Algebraic Type Command)
o renamed proof obligation to Sequent
o took care of commenting out unused definitions in UnitB.FunctionTheory
o fixed some warnings (unused definitions and imports) in continuous
o in compile and run_test, added the -threaded option for test and continuous
o added a Prover interface which manages worker threads
o it is used transparently by discharge_all