Added some more options for source selection
Changed the way the scene selection code works, thanks to:

http://www.eventghost.net/forum/viewtopic.php?f=9&t=3382#p26822
Added a CursorAction which allows the user to send various commands such as Up, Down, Menus, and more.

Special thanks to Dragon470.
Any wx.Choice actions are now remembering the last used option.