code re-writes

[Ivan-Johnson]

make PhysicsEngineRunner prettier; eg.
make PhysicsEngineFrame with ContainingPanel nested (inner? the non-static one.) class & move ~All of display panel there. make separate branch during rewrite via team-switchTo-new branch?
http://stackoverflow.com/questions/16529390/how-to-create-a-new-remote-branch-with-egit
http://wiki.eclipse.org/EGit/User_Guide#Configuring_upstream_push

also, make PE's settings panel use setting panel in Helper

also also, replace world borders with walls