Adding Limitate Clause

http://www.smogon.com/forums/threads/balanced-hackmons.3489849/page-93#post-5908613

-ate abilities are only limited to 1 per team, total (so no Aerilate + Pixilate or double Aerilate). I believe I did what you asked me to do to make the code look nicer in a later post, @Slayer95. 

I've tested this by setting up: A Pixilate and an Aerilate Pokemon, 2 Aerilate Pokemon, 3 Aerilate Pokemon, and An Aerilate + Magic Bounce Pokemon. The last one was the only one without any errors (as in illegality issues, not actual js errors), and the rule dialog popped up as it should at the start of the battle for the last one as well (with all the others). 
Remove the <code>else</code> token. It's not needed as the function is returning when <code>ateAbility</code> is trueish.