Sort albums in rotation by date last moved

[bentsherman]

In the Library Control Panel, it might be useful to order albums in rotation by how long they've been in their current bin. That way the music director could easily tell when albums should be rotated. For each album you'll need to store the date that it was last moved (something like date_moved), and then on the client side you could just display the date or compute the time difference between then and now.

[bentsherman]

The date_moved field has been added, now the list should be sorted by date_moved and possibly transformed to show the number of days since last move.