Lots of fixes and updates

I finally got around to fixing the targeting systems on the turrets, so now when you click on SLOWEST etc., the turret will actually function.

I've started implementing damage modifiers and damage combinations. Enemy will respond to different turret effects. The boss enemies, the super slow ones, do NOT like ice. They'll take double damage from Ice.

Coming: if you shock a mob that's frozen, you'll get a nice bonus to damage.  Many other combinations like this will be added.