GamesHandler: Implement vote-to-?start and ?wait commands

Implement a vote-to-start mechanic and a ?wait command to help limit ninjastarting, a la lykos.

Note: First version of Secret Hitler (and GamesHandler) is currently feature-frozen and held for final revisions, bug fixes, and code review before publishing.  This issue is deferred until after this first version is code reviewed and published.  See #22 and #20.
