Refs #44 - Remove default sorting
Merge branch 'master' into remove-default-sorting
Refs #44 (github) - Add upgrade step for default sorting

- In order to keep backward compatibility added an upgrade step that
  adds a sorting widget by effective date (reversed) for all Faceted
  Navigable items that doesn't already define sorting.
Remove default object_provides widget for new Faceted Navigable items
Refs #52 (github) - Fix sorting for new-style Collections