Fixes to purge spurious error messages from logs

	modified:   Callback.py
	modified:   Control.py
	modified:   FitsImage.py
	modified:   gtkw/plugins/Histogram.py
	modified:   gtkw/plugins/Pan.py
	modified:   gtkw/plugins/Preferences.py
	modified:   gtkw/plugins/Zoom.py
	modified:   icons/ginga-splash.ppm
	modified:   qtw/QtHelp.py
	modified:   qtw/plugins/Histogram.py
	modified:   qtw/plugins/Pan.py
	modified:   qtw/plugins/Preferences.py
	modified:   qtw/plugins/Zoom.py

- fixes to purge spurious error messages from logs
  - this cleans up most (almost all) of the spurious error messages cluttering
      the logs
- updated splash image for 2013
- fixed a bug where zoom image was not resizing while adjusting radius control