First implementation of hbz_id validation

- references #417
Moved client side js into right position

- references #417
Only show first spinner of ul's

- references #417
New sort option for volume count
Rename task to clear the response cache.
Make sure params will survive when creating searches.
Fixed some styling.
Median Primo records should be a bit more ActiveModel.

This is important to make AtomFeedHelper work with Median Primo Record
objects.
Add RSS feeds for search results.
Add RSS feature for search results.