Implementing H2: Player Ladder Discs - Opponent Ladder Discs

ToDo: 
integrate polarity block detection
implement isPolarized method

Changes: in progress.
Implemented method isLadderBlocked method. Untested.
Finalized H1 and H2 heuristics.

Todo:
Validate that polarity check on sides is not necessary for heuristics.

Changes:
Added polarity check for polarity blocks (and neutralized blocks -- with
base). These checks cancel the point value of a ladder on H1 and H2.

Passed tests.