Implement basic collision detection

[ellenhp]

Everything should be a capsule or rectangular prism for now.

[ellenhp]

This should probably all happen on the server. I don't think I'm worried about bullet-through-paper issues for now, but that could change.

Using a brute-force N^2 broadphase should be fine for now since I don't know how to implement anything else in spherical coordinates. But I can't decide on how to represent vessels for the nearphase detection, or whether vessels should be allowed to decide how they're represented (capsule, box, etc).

One thing I'm not concerned with is the performance of the nearphase detection, since that should almost never have to run.

[ellenhp]

I think mapping every nearphase detection to cartesian coordinates is the right choice.
X = R * Longitude * cos(Latitude)
Y = R * Latitude
Z = Altitude

This allows traditional geometry intersection tests to be used. A capsule-capsule intersection test should be fairly easy to implement this way. And it'll be close enough. Vessels aren't big enough that it'll matter.