Misc bug fixes

	modified:   Control.py
	modified:   FitsImage.py
	modified:   Mixins.py
	modified:   PythonImage.py
	modified:   gtkw/GingaGtk.py
	modified:   gtkw/GtkHelp.py
	modified:   gtkw/gtk_rc
	modified:   qtw/QtHelp.py
	modified:   qtw/plugins/Log.py

- fixed a problem with an uncaught ImportError if the pilutil module
    could not be imported (PythonImage)
- fixed a bad gui call in qt version of Log plugin
- added a new pair of callbacks to the Desktop class in GtkHelp