Renaming solver-related command-line options in order to decouple them f...

...rom STP. More specifically, command-line options max-stp-time, use-forked-stp and stp-optimize-divides renamed to max-solver-time, use-forked-solver and solver-optimize-divides, respectively.

Option of running the SMT solver in a separate process (i.e. forked) set to true by default.

Options of running SMT solver forked and with optimized divides made available to Kleaver as well.