Move and Shoot Performance Logging Tweaks

Move and shoot functions now use CvStopwatch performance-measuring
functions, like all other Civ5 functions.
Fiddly Archers Tweak

Siege units will no longer be fiddly and reposition plot performance
logging is now relegated to GetMovablePlotListOpt().
Siege Move and Shoot Fix

Siege units will no longer move and shoot if they cannot set up as well
as fire after moving. Consequently, siege units are now fiddly again
(ie. they will always move and shoot when possible, even if they are
already in range).