Minor changes to drone borg sprite.

Fixes the 'drone' sprite for borgs.  The eyes are now actual eye sprites instead of attached to the base sprite.  No more pumping 40 shots into a secborg and wondering why it won't die.

Adds option for medical module to use the medical drone sprite.
Adds sprite for surgery and mining.  Mining will no longer use a medical sprite (why???).  Surgery is recolored to white/red from white/green.  Mining is brown/purple.