Overhaul of the community list code.

From a user perspective: Use friendlier URLs for lists. Reuse the
search results table for displaying lists. Simplify the management
pages and improve the search rule UI to help fill in the values and
validating them, instead of just providing a text field. Fixes ietf-tools#1874.
Add an explicit button for adding individual documents. Include all
changes in the document change streams, not just some changes. Fix a
concurrency issue that allows changed documents to escape the search
rules. Don't create an empty list just be logging in.

From a code maintenance perspective: Clean up the models. Replace the
background caching scheme with direct queries. Get rid of a big chunk
of code. Speed up the code that adds track buttons to search results.
Add tests of all community views. Fixes ietf-tools#1422. Also fix some minor
bugs and oddities here and there.

There's still some work to do with respect to integrating the group
lists better.
 - Legacy-Id: 10921

Author: OleLaursen