Patch queue functionality

[bonzini]

• Basic support in database and web interface
• Add "queue:XXX" to search query
• Allow downloading queue as mbox
  • Add /my-queues/PROJECTNAME, which automatically restricts the my-queues query to a project
  • Add /my-queues/PROJECTNAME/NAME to format queues like search results
  • Add /my-queues/PROJECTNAME/NAME/mbox view, similar to series mbox view
• Allow emptying a queue from the my-queues page
• Per-project WatchedQuery
• Sanitize queue names
• REST API improvements
  • Expose queues in REST API as /projects/.../queues/...
    • PATCH/POST/PUT on series can add/remove series from a queue
    • Add mbox_uri in project queue view
  • Expose watched queries in /users
  • Add mbox_uri to SeriesSerializer, redirecting to mbox view from www/views.py

[elmarco]

@bonzini there is a wip branch for this? thanks