toward pulibrary/pul-store#44, folders can't pass qc w/o core elements and pages
added  self.use_relative_model_naming? true so that dynamic methods and routing are less messy;
Toward pulibrary/pul-store#40. Needs feature test.
fixed wrong :class_name
can always belong_to a PulStore::Item
merged
page belongs_to exactly folder OR text; enforced with validation
done, but tests not yet updated;
trying to figure out before_destroy
toward pulibrary/pul-store#53
Merge pull request #1 from pulibrary/delete_enforcement

Delete enforcement
resolve merge conflict with development in base.rb