Rotation

Started implementing rotation for physics objects. This will lead to
angular momentum and swinging objects attached to other objects. There
are still a few bugs. Specifically, surface pushback causes bouncing at
different angles. This will need to be adjusted (not by decrementing the
pushback, but by adjusting how it is applied).

At this point, I'm still using rectangular collision. I'm calculating a
rectangle around my rotated object that uses the maxima of the vertices
as the top, bottom, left, and right. That will allow the surfaces to
continue to work as they do for now. Later I may need a more robust
method, but I think this will continue working for now.

There are a lot of images to go with this commit. I'm starting to work
on some animations for the game. They need a lot of work, but they're
something to start with.