Now that we don't have the OpenGL1 option any more in ParaView we
can get rid of the specialized proxies' definitions in
proxis_opengl2.xml by moving them into views_and_representations.xml.
Consequently, the "Extension" stuff for representations in
proxies_opengl2.xml have just been put directly in the proper spot
in view_and_representations. This helps the Catalyst editions since
the catalyze.py script didn't properly handle the Extension stuff
anyway.