When using the VimEditingEngine in the TextEditor, vim's mode and the previous key are shown in the editor's statusbar.
Add the functionality of key sequences 'cw', 'ce', 'cb', 'dw', 'de' and 'db'.
Implemented move_to_beginning_of_next(), move_to_end_of_next(), move_to_beginning_of_previous() and move_to_end_of_previous() functions for more correct word jumping than the move_to_xxx_span() methods that were previously used.
