Update Copyright Notice

I re-spaced it, and changed the version from vis9a to vis9c.
Add Shortcut to "Add Combination" Button
Better Error Handling during an Experiment

- They won't crash vis, but they will be reported to users!
- Also some minor changes to comments in experimenter.py
Hide "Cancel Operation" Button When Performing an Experiment
Improved Experiment Settings Selection in GUI

- Non-applicable options use setVisible() rather than setEnabled(), so it's
  more clear (especially on OS X) that they aren't possible choices.
- When changing output object, a valid output format is automatically
  selected.
Fix "All Voices" and "All Voice Pairs" Checkboxes

Now they behave exclusively, and cooperate properly with other part
selections.