Implemented the pseudo-code high-level functions for
PropNetStateMachine. These functions do not currently work since value
propagation still needs to be implemented.

Adapted ProverStateMachineTests for the PropNetStateMachine.
Compute proposition ordering to propagate truth values. Terminal
proposition does not seem to be updated correctly.
Additional changes to propnetStateMachine - TicTacToe now seems to work,
however games like Connect4 still have issues.
Modified PropNetSM to use OptimizingPropNetFactory to generate propnets
with seemingly fewer errors.
Integrated Bertrand's speed/correctness testers.

Current PropNet speed on Connect4: ~5500 ops/second
Current Prover speed on Connect4: ~1000 ops/second
Merge branch 'propnet_exp'
Added in ability to use PropNets with MCTSGamer. Modified MCTSGamer to
run depth-charges in parallel (when using Prover state machine).

TODO: Asses performance impact of running multiple depth charges.