Added basis for server-side cooldown checks, added warmup checks, closed #273

Note that cooldown check is currently used only for the holoemote
command. To add a cooldown to any command, all you have to do is
CreatureObject.addCooldown(name). In this commit I also moved some
cooldown variables from CombatCommand to BaseSWGCommand since many
non-combat commands had cooldowns (Wookie Roar, Holo-Emotes). I also put
in a warmup cooldown (time before command is called) for non-combat
commands.