save play_controller.init_side_done as a toplevel attr of snapshot

This is an attempt to fix bug (insert correct number here) wherein mp games could be corrupted when saved, by not storing the init_side_done value, which caused the "upkeep" (or "refresh") event to be skipped for the turn of the side that disconnect. This was very annoying as it means that players would not get gold for that turn, their units would not heal or get full moves for the turn.