Too many changes to list.
Addresses https://github.com/JetBoom/zombiesurvival/issues/122
Players are no longer implicitly zombies if they're not humans. Players are no longer implicitly humans if they're not zombies. This is preparation for a third, optional spectator team. A few small optimizations and fixes.
Consider possibility of nil or NULL being a value in the tables returned from util.FindInSphere, util.FindInBox, and ents.GetAll.
