Fix for Bug report #756  

Add a supplementary BattleActionType parameter to BattlescapeGame::checkReservedTU.
Rich BattleActionType  with BA_KNEEL and BA_RAISE
Perform proper tests also considering actions when validating reservations:
If kneeling, do not consider kneeling reservation. If already kneeled, do not consider reservation on underflow test, and neither on any move other than raising.
Add as appropriate the new parameter on various calls (BA_WALK and BA_TURN as actions - OK as long as not messingwith KNEEL or RAISE)