Added resourceName attribute to Class. Classes now save their name relative to xmfHome so that
(providing xmf.xmfHome() is set to xmf-src at startup) it is possible to navigate to the
source file for a class definition. Added a browser menu item for this. Double clicking on
a class in the browser will now bring up the source file for the definition of the class
providing that the class definition exsists in a single file.