Fix: Stream showing reply annotations without their parents

If new annotation data arrives via websocket, the applyUpdates()
function processes it and injects the new annotation data into our
client-side annotation-db.

Some annotations (depending on the viewstate) are put immediately into the viewer
by adding them to the $rootScope.annotations

However, in the case of the stream page reply annotations can arrive without
their parent annotation, and because that they didn't get inserted into
the rootScope and thus never displayed

This commit fixes that, by letting these annotations inserted into
the rootScope.annotations for document viewstate (which the stream uses)