UndoCommands: move the implementations of virtual functions of template classes to UndoCommands.h due to bogus MSVC warnings: http://connect.microsoft.com/VisualStudio/feedback/details/778490/implicit-instantiation-of-virtual-template-method-causes-confusing-warning
Add PhysicsWorldPtr and PhysicsWorldWeakPtr typedefs for convenience. + Couple minor TODO additions.
Fix bogus error print if server was started without --protocol.