[Changed] how lair buildings are chosen when spawned
[Changed] creature destroy missions now spawn the same number of mobs
with each wave
[Changed] number of mobs spawning at a destroy mission now varies based
on the difficulty of the mission
[Changed] number of mobs spawning at a theater now varies based on the
spawn's difficulty
[Changed] max condition of lairs is now somewhat randomized

Change-Id: I165978e39b433feaf8e06bf52825f47f019302bd