COMP: Move "Slicer3Adapters.tcl" into "Python/slicer/tcl"

The historical folder GUI that was specific to Slicer3 had been removed
and "Slicer3Adapters.tcl" has been moved to a more suitable home. It is now
copied/installed as a python resources available within the python
directory.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21766 3bd1e089-480b-0410-8dfb-8563597acbee