Implement ArcBall for Camera / add MouseViewController

[cjcliffe]

It was suggested here:

http://www.cubicvr.org/index.php?option=com_fireboard&Itemid=62&func=view&catid=5&id=205

That we should implement an ArcBall / Trackball

http://viewport3d.com/trackball.htm

Might also be good to learn from MouseViewController in CubicVR.js and implement something similar that's easy to use with GLUT/SDL