flipped direction of last air battle. hostile come in from the coast, no longer from the ocean. moved last spawn checkpoint so players don't spawn in combat

minor changes to add spawn variety to the last airbase players attack. planning on randomizing SAM sites too, but that will take a little more time to make that trigger system.

minor update, small adjustments

added a trigger system to make sure easy mode dosen't get triggered during an aircraft intercept becuase someone dies just before the wave starts.