MIGRATION: Added "Archived" status.  Does not really alter the schema - look closely before migrating or rolling back.
LTSINSCRIP-56 - Reservation notices are generated for new ReservableAssetTypes in after_create on RAT

This probably isn't all that needs to be done.  Ideally, having some sort of mechanism for handling changes
in statuses would be better.  Also, I'm still not sure I like it killing existing statuses.  I'm adding an
issue to revisit this behavior with Anne Marie; something sane like "generate for everything that doesn't
already have one" would be nice.
Minor form tweaks for RAT