Introduce Game class

Adds a class for all the main game mechanics, and transitioning the state
Also imports OCMock to mock out the state.
Use forward classes

Pulls the classes apart a little by only requiring that the type is used,
not the full API.
Basic checks for mystic/corrupt

Handles the most basic checking for mysticism and corruption for the
clairvoyant, medium and wizard
News from the inn?

Updates the NewsFromTheInn on the game state when we check for corruption
as a Clairvoyant.

This currently doesn't handle the case where the clairvoyant checks but
the Bard/Innkeeper is subsequently killed or made into a minion before
morning.

Also adds some utility methods to the game state to extract a player
given a role, or to check if a role is still in play.