Reduce the perceived loading time in the notebook by fetching
annotations in, roughly, the reverse chronological order in which they
are displayed.

By default `SearchClient` fetches annotations by ascending creation
date. This makes sense in the sidebar as it typically correlates,
roughly, with the order in which the sidebar presents annotations by
default (document location order). For the notebook however this is
suboptimal.

 - Add `sortBy` and `sortOrder` options to `SearchClient` and
   `loadAnnotations` to control fetch order, with the defaults remaining
   the same as before (`created`, `asc`).
 - In `NotebookView` set `sortBy` to `updated` and `sortOrder` to desc
   to fetch annotations in reverse chronological order.