new attempt at the editor
basic document handling
implemented view/document closing
added main menu and implemented new view function
display view indices in title bar
added undo stack and undo/redo actions
added test command
track document modification state and display it in the top level window title bar
implemented a dummy save function (does not actually save anything)
implemented edit locking (used during saves)
added progress tracking
clean up properly after closing a top level window
preparations for multiple parallel progress-type operations
added operations progress bar
implemented world verify function (doesn't do anything yet; mostly meant as a test for multi-operation interface)
added new document function
minor documentation changes regarding future improvements and additions
added UniversalId class
basic sub view system (very incomplete)
Merge branch 'master' into editor2