Adds Atlantiscze's custom borg and AI sprites.

![my_borgsprite](https://cloud.githubusercontent.com/assets/6371075/5235765/dbb8678e-77d6-11e4-8f49-0c1034e19c3b.png)
Approved here: http://baystation12.net/forums/viewtopic.php?f=33&t=11683