Fix GWT build.

GWT does not have support for Class.getSimpleName(), use a hard-coded
string instead.

See http://code.google.com/p/google-web-toolkit/issues/detail?id=3404
for more information.

GWT does not have support for String.format() either (wtf?).
Fix MapPhysicsManager size issues.
Add player physics.

It's a bit hack-y, but it sort-of works.