Cleaned up SDL mouse for FPS

* no more "drift" if you pick up your mouse
* mouse is properly grabbed and hidden (toggle with 'L')
* Q to quit (since P is used for wireframe mode already)

also:
* GLMesh consistent with trim and convert_path on filenames
* shipobj/ship.mtl removed extra newline so it no longer commplains that materials can't be loaded (ship still has no texture though...)