Documentation and code cleanup.

Changed all non-public methods in CardGame to protected. Changed all nested classes in CardGame to private. Moved "join" command back to CardGame. Changed loadHouseStats() and saveHouseStats() to loadGamestats() and saveGameStats(). Added game rules and game stats strings to strlib. Added more documentation.
Documentation and code cleanup. (issue #34)

Changed Player and Hand classes as nested classes of their respective games. Removed README. Added GameManager interface for usage of the package by other PircBotX implementations. Updated scopes for some nested classes.