Lots of changes to massively simplify things and make them much more
performant.

- The thread directive gets a few changes
  - Cleared up confusing tuple unpacking in favor of named properties
    in the render queue as per the suggestion of @aron
  - The replies and annotation are set at once. Since the replies in
    turn render lazily, this should be fast enough for all but an
    unwieldy number of threads. If we hit that wall, we'll have to do
    some filtering / pagination.
  - The directive is now triggered only on attributes and parses the
    attribute value to get the thread
- The threads are rendered from a single thread root rather than using
  a global list of annotations that must be watched for its threads to
  be extracted. This results in a huge performance gain because this
  thread container has a stable set of children.
  - When the first `annotationsLoaded` callback arrives, we set a new
    root from the result of asking the threading plugin to thread them
  - Lots of hackery during store reloads goes away because we just nuke
    the thread root and reload
- The application controller does not have to modify a root annotation
  set at all anymore
- Use of the root scope in the controllers goes away entirely
- The ongoing edit is now stored in the scope again so that it can be
  be pinned to the top of the thread list
- The editor view and controller go away completely because the top
  level edit is now pinned to the top of the list, removing the need
  to re-render annotations between editing and viewing
- The selected annotations are now a hash of annotation ids to true
  values if the annotation is selected, or null if the selection is
  empty
- An ng-show is used to show/hide the selected/unselected annotations,
  further reducing re-renders
- The view state is gone complete and now there is only sort
- The sort is not applied programmatically in the controller, but a
  simple watch on the name of the sort is used to set the predicate
  and reverse settings as scope properties that feed into an orderBy
  filter on the thread list, reducing the number of extra watches we
  have to do and further reducing the code
- The sort is no longer an animated dropdown, but sits at the top of
  the list always (I assume we can style this better, so have at it)
- Unnecessary helper and logging functions are removed from the
  annotator service because silence is golden