Add top-level wrappers to the management pages

Containers analogous to #yarr_con on the list_entries page, named for
the associated templates.
Added js mark all read button

Also several bugfixes:
* Fixed "No more entries to load" status message and "No items" entries message
  appearing at the wrong time (``Entries.loadNext``)
* Fixed list mode click having incorrect effect (``Entries.current`` now nulled)
* Fixed long-term scrollTo error (top margin was calculated incorrectly)
* Unread count updates correctly when marking all read (querysets are lazy, so
  ``EntryQuerySet.feeds()`` was returning an empty qs after ``.update()``)
* Fixed dropdown bugs - clicking on child elements now works, and they open
  when the control bar is fixed
Loading a feed updates the unread count
Rewrote unread count code
Added yarr_clean command
Corrected API set state call to get new unread count
Merge branch 'management-wrappers' of https://github.com/twm/django-yarr into twm-management-wrappers