Save off changes before heading down a different path.  Some aspects of the
Create Rehearsal Plan dialog are working, but they're sufficiently complex
to justify a more general solution.
Creating the list-selector component.  Currently uses a simple select input
to manage the lists.
Mostly got the ListSelector to work with divs instead of select.
Behavior of list-selector selectable list is done.
Moving items between the lists in the list-selector now works.
The selected lists are kept sorted by the sort key.
Learning songs are now on the dialog.