WIP Overhaul view and sort behavior

Big changes to view, sort, routing, filtering, etc, etc, etc...

Todo
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- [ ] stream search -- race between $scope.updater and stream controller, need to send the filter
- [ ] forced login -- a comment about ideas for that [here](https://github.com/hypothesis/h/issues/1020#issuecomment-53400218)
- [x] page search -- simple matter of fixing the ugly ng-show conditions at the bottom of the viewer template perhaps with more verbose, obvious variables, or scope/controller functions to abstract the route details from the template a bit
- [ ] Check on https://github.com/hypothesis/h/pull/1436#discussion_r16705832
- [ ] Restore "no results for “query”" message.

This looks like it will only ever set `threadRoot` the first time this runs. Need to check, as currently the stream search doesn't update.