Allow document search to be filtered by type and subtype
Tweak form label based on styleguide
Include link back to edit announcement when present on publications

This is only displayed for pre-published editions as once they have
been published, the announcement is redundant and shouldn't be visible
on the site anymore.
Allow additional filter params to be passed into the document finder

This allows us to perform a narrower search, for example just
publications of type statistics.
Use document finder to assign documents to announcements