TODO
====

* Form sort criteria

* Add single selection (pulldown, radio) criteria (davisagli)

* Fix folder_contents view to support deleting, etc.

* Use subcollections to support AdvancedQuery operations

  Collections will act as grouping/parenthesis *and* operators.  IOW,
  a collection will have a boolean field to set whether it uses AND or
  OR to find the intersection or union of its result sets.
  Sub-collections will not acquire criteria but instead parent
  collections will treat sub-collections as criteria groupings.  Not
  yet sure how to handle sorting.
