1.0 Alpha 1 - Do not use for serious work!!!, expect bugs

New major Feature: Undo / Redo, including structural changes

• Implemented new event propagation system for propagating changes in transcription.
• Reworked UI to use this system
• Undo/redo features are based on these events

Command system cleanup

• I found a way to remove command bindings from AvalonEdit
• all the unused and conflicting commands should be found, removed from the AvalonEdits in the Element control and hacks used in editor_PreviewKeyDown/up should be deleted
• pageup/pagedown is probably handled in the main Listbox in speakersVisualizer, it should be removed too