Quality of life improvements

Still figuring out how to make the Player be invulnerable after being hit.  It KINDA works, but there are still kinks to iron out.

Enemies also die more consistently now. We STILL need to make their Shield and Vulnerability parts more clear and visible. But we added a different sound effect when the light orbs bounce off the shield.

Also, the lightorbs no longer push the enemies away.

Minor rigidbody changes to deal with some of the sliding. Work in progress.