Camera refactor

Splitting the camera frame setup and some other bits out into a separate class, so that things that need to work against the camera frame (speed lines, trails, later cockpits) can do so without need to rely on the camera update/draw cycle.

Also did a bunch of internal cleanup, most significantly removing the old spike code in favour of billboards. This is probably the most contentious change, and the one I'm happiest about dropping if people get grumpy about it. Though I'd prefer improved math and/or textures to getting rid of it entirely if possible. If not, just drop the last commit.

There might still be a bit more to do on this. I'm a little lost because I stopped work on it for a couple of weeks and don't quite remember where I was at. I've brought it up to master with some difficulty and I'd like to merge it now so it doesn't rot again.

More info about where this fits into the bigger plan: http://pioneerspacesim.net/forum/viewtopic.php?f=4&t=118