Reduced default physics density from 10.0f to 1.0f and bug fixes.

This release fixes up some remaining regressions and adjusts the default physics density.

The adjustment to default density is extremely important because it will heavily alter the physics of any entity that uses it. You will either have to make your entities explicitly the old 10.0f value or reduce the forces applied to it by roughly 90 percent.

Despite the potential user impact, this was a very important change to make because the required force vectors to move anything were huge and threatened precision issues down the road for bigger entities.

That's about it for this release. As usual, make sure to update your Nu.Game template!