Adding a special user module to VITESS

For a general description see InsertModulePolarizer.pdf 
in the WWW subdirectory.

Starting from version 2.1 itīs even simpler for the GUI part.
Just add a file usermodule.tcl in the Vitess directory
to add some module(s) to the VITESS GUI. As a starting
point you may begin with the example file usermodule.tcl.txt.
