Make turrets use projectile-appropriate SFX

Fixes #5030
Build /-tg-station/master, spawn as captain, walk over to AI, set the turrets to Kill and open the door. They'll play taser SFX. [Here's a clip as proof](https://dl.dropboxusercontent.com/u/11223021/dreamseeker%202014-10-06%2021-59-18-251.avi)