FR: Enhancements to ship maneuver sexps

Probably complicated: Allow turrets to acquire and fire at targets independent of ship orders. I'd want this to still accept the turret specific sexps, eg ability to force a target for a turret or stop it from firing entirely. This is so that turrets are able to fire while a ship is using play dead to allow maneuvers to work correctly.

Probably less complicated: Roll until level boolean for maneuvers. This would allow for a ship to roll along its Z axis until level with the game world's. This will obviously not work right and probably have weird effects if you try to use it on a ship moving along the Y axis, but for ones moving level to X/Z it should be fine and make certain cinematic movements much simpler to fred.