commands which needs undo/redo support

SongEditor:
 + Add/remove pattern to sequence                       | done
 + Move pattern list item by drag and drop              | done
 + Move patternlist item by clicking up/down buttons    | done
 + Clear full pattern sequence                          | done
 + Delete pattern from list                             | done
 + Copy pattern                                         | done
 + Edit pattern properties                              | done
 + Load Pattern from context menu                       | done
 + Drag and drop pattern from library to pattern list   | done
 + Fill/delete pattern sequence                         | done
 + Edit virtual Pattern                                 | ----
 + Move selection (pattern sequence)                    | done
 + Copy and move selection (pattern sequence)           | done

Time Line:
 + Edit timeline tempo                                  | done
 + Edit timeline tags                                   | done

Pattern- & Piano Roll-Editor:
 + Add/Remove note Pattern Editor                       | Done
 + Add/Remove noteoff note Pattern Editor               | Done
 + Edit note length Pattern Editor (right cklicking)    | Done
 + Add/Remove note Piano Roll Editor                    | Done
 + Add/Remove noteoff note Piano Roll Editor            | Done
 + Add/Remove note via Midi                             | Done
 + Destructive recording (Delete Notes)                 | Done
 + Edit note length Piano Roll Editor (right cklicking) | Done
 + Edit velocity Piano Roll Editor                      | Done
 + Edit pan Piano Roll Editor                           | Done
 + Edit lead lag Piano Roll Editor                      | Done
 + Context delete notes                                 | Done
 + Context menu fill notes                              | Done
 + Context menu random velocity                         | Done
 + Drag and drop instruments order                      | Done
 + Context menu Delete instrument                       | Done
 + Drag and drop intrument from library                 | Done
 + Main menu Add instrument                             | Done


Note properties ruler:
 + Edit velocity                                        | Done
 + Edit pan                                             | Done
 + Edit lead lag                                        | Done
 + Edit note key                                        | Done

Mixer:
