Add show route and refactor authority/controller interface

Added an item show route, and changed the interface between the authorities and the controller. Making a new authority object will no longer do a search---call #search
to do that. Can also call #get_full_record for show information.

Also did some refactoring of the individual authorities.

More tests on the show route are needed. I wasn't sure how to test it. It seems that each authority should test its own web interface.

All comments are welcome.