Added skeleton for Checkpoints.
Basic checkpointing for Z3 with a simple test.
Throw IllegalStateException when no checkpoints.
Added documentation to the CheckpointableSolver interface.
Need to null out the checkpoint stack on free.
Need to specify sat tactic for Z3 solver.
Add checkpointing to Bool2CNFTranslator.
CheckpointableSolver needs to be a public interface.
Added checkpointing to translations and solver.
Need to use Eval with model completion.
Checkpointed GIA and bugfixes.
Use CGIA by default. Add assumption to solver test.
Fixed the CGIA.
Expression Caching for Z3.
Added the capability to copy a MiniSat solver.
More work on checkpointing MiniSat.

Still doesn't work.
Fixed copying of MiniSat solver.
Removed debug prints from MiniSat.
Remove debugging info from minisat.
Expose status checkpointing to NativeSolver implementors.