Allow to open inventory based on another criteria

* Together with categories, allow to filter by the product's
  manufacturer/brand/family
* Make 'include uncategorized products' an option on category tree
* Improve get_unblocked_by_categories to only make one query
* Add a new api to get distinct values in a Domain object

Change-Id: I217bc1a58e1e0c2d478ef2b8038ce8b2dad83ea4
Fixes: http://bugs.async.com.br/show_bug.cgi?id=5550
Merge "Allow to open inventory based on another criteria"