Slow discovered that the migration that creates CatalogEntries blows up if you had
existing SuggestedDeployables. We had talked about not doing the whole dance to port
everything forward, but didn't intend for it to blow up where it did.
If you are migrating a database with SuggestedDeployables, we will create a default
catalog (if no catalogs exist) and assign them to that catalog. Otherwise the migration
fails because we try to save nil values to a column that can't be nil.
I also got sick of trying to remember how to look up the 'default pool' metadata
object, so I added a Pool.default method to do so.
-- Matt