Reef replacement.

Contains models, script, unitdef, gadget changes. 
Lacks buildpic for now, because icongen hates me. 
- 91 and 98 compatible .dae 
- fixes #275 
- fixes armcarry corpse misbehaving in 98
- drone gadget allows parallel spawning of drones 
- drone gadget allows animations on drone spawn and launch
- weapon works, antimissile not yet tested
- includes deathclone
- includes death anim
- old armcarry unitdef kept and untouched
- strider hub build option changed to "reef"