SOCGameHandler.handleCANCELBUILDREQUEST(INV_ITEM_PLACE_CANCEL): Send game state; javadocs
State PLACING_INV_ITEM: SOCHandPanel allow Cancel (Play Card button); javadocs
State PLACING_INV_ITEM: SOCHandPanel.updateDevCards +addedPlayable; fixes bug where inventory list appears disabled after that state