Groundwork for kittens.
Added kittens and Proc, sprites by Nienhaus.
Added Nien's improved new cat sprites.
Merge branch 'master' of https://github.com/tgstation/-tg-station into kittens

Conflicts:
	code/modules/mob/living/simple_animal/simple_animal.dm
Merge pull request #2149 from Miauw62/kittens

Kittens!!!! !!! !! !! !!!!!! !