Fixes #20: Pass should show a message
Now shows a dialog warning the opponent has passed and prompting to pass as well or continue.
This commit also includes some refactoring that was necessary for the change:
 * gameChanged now passes a Bundle with some additional info if needed (type of change or precisions such as player_passed, player_played for now)
 * a Player now has an avatar instead of just a name which make the association with the black or white stone icon cleaner and opens the way to displaying a Google Plus Avatar.
Code Review Amendment
 * Replaced the pass message dialog by a message in the a message area in GameActivity
 * Kept avatar system but not using it for Stone display which represent the player Color, not its Avatar
 * Introduced GoPlayer as a subclass of Player containing a StoneColor
Code Review Amendment
 * Removed the info Bundle
Code Review Amendment
 * Removed the info Bundle
merge master changes

Conflicts:
	src/com/cauchymop/goblob/GoGame.java