Improved autoeditor menuing.

Extended Autoeditor to contribute target class name as breadcrumb in certain
circumstances.

Example: notice there that breadcrumbs continue all the way down to the tempo
object contained in the tempo inventory:

    Red Example Score (2013) - materials - 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)

    |> 4

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

       1: duration (d): 1/8
       2: units per minute (pm): 135

          done (done)
          set to none (none)

    |>