Adds generic impact noises to all projectiles

Overrides these generic sounds with more suitable ones for electrodes and beams.

sear.ogg is a flesh sizzle sound effect for beams
tase.ogg is a crackling electrocution sound effect for electrodes

[![Video](http://puu.sh/6xco9.png)](http://www.youtube.com/watch?v=I2R4pfXP2ro)