Issue #163 Combined objective and rule panels

Everything is in one class and window now. Serious refactoring to
simplify the code and allow for simpler rule modification. Removed
extra unneeded JPanels that were only being used for adding labels, and
changed all layouts to be gridbag for conistency and simplicity.
Fixed issue #164 that wasn't allowing anything but Kings or Knights as
the objective piece for games.
Merge pull request #166 from jmccormi/objective_fixes

Issue #163 Combined objective and rule panels
Moving Game, Board, Rules, Square, and Piece to a new "models" package, with the goal of eventually following the MVC pattern