Autoeditor now publishes state in (EDIT) versus (EDIT+).

Autoeditor tracks target state. When target has changed the (EDIT) breadcrumb
changed to (EDIT+).

Use of (+) to denote change is taken from Vi.

Example:

    Red Example Score (2013) - materials directory - tempo inventory (EDIT)

       1: 8=72
       2: 8=108
       3: 8=90
       4: 8=135

          elements - add (add)
          elements - move (mv)
          elements - remove (rm)
          editing - done (done)

    |> add
    Element]> ((1, 8), 136)

    Red Example Score (2013) - materials directory - tempo inventory (EDIT+)

       1: 8=72
       2: 8=108
       3: 8=90
       4: 8=135
       5: 8=136

          elements - add (add)
          elements - move (mv)
          elements - remove (rm)
          editing - done (done)

    |> rm 5
    Elements]> 5

    Red Example Score (2013) - materials directory - tempo inventory (EDIT)

       1: 8=72
       2: 8=108
       3: 8=90
       4: 8=135

          elements - add (add)
          elements - move (mv)
          elements - remove (rm)
          editing - done (done)

    |> q