Clean up UI code.

- Use Bind instead of connect. It's recommended for anyone using wx 2.9+
- Remove AppConnector. All this did was destroy objects used in the UI. However, wxWidgets handles this. So it's redundant.
- Misc other unimportant changes.
Correct event handlers to trigger in all instnces

Some events don't propagate correctly to the right sub-window
and some things like the pad handler don't even necessarily have
windows. So, just register some events with the top-level app.

Also add a virtual destructor to the PadHandlerBase to be able to
deal with multiple inheritance in the derived classes.
Merge pull request #185 from lioncash/gui-cleanup

Clean up UI code.