Add favourites landing page

I added a few lists (dev/user/commits) from two projects (ranger/atlas) to my favourites in ponymail.
I figured I'd add a browser bookmark to go to my favourites, but realised adding a favourite just adds them to a menu in ponymail.

I believe it would be useful if there was a "favourites" page in ponymail whilst lists the groups I've favourited - and perhaps with a simple summary such as last posting date, and of course a link to open the regular list page.

Start by locating the existing favourites menu and regular list page in the JavaScript application. Confirm how favourited groups are stored and rendered, then define the page around the requested group summary and links. Done means the favourites page can be opened directly as a bookmark and displays the user's favourited groups.

Written by the indexing model from the issue text.