Enhance selects on stats release announcement form
Extract and enhance document finder JS to make more generic

The primary change here is to also set the edition_id as well as the
document_id if the input field is present. This will allow the code to
be reused when linking statistical release announcements to editions.
Enhance Admin::EditionFilter to allow filtering by multiple sub-types
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
ReleaseAnnouncement provider, model and controller
Fix destructive helper method
Stub release announcements visible on frontend
Release announcement organisations are objects
Announcements can be filtered (rummager stubbed)
use real examples in rummager stub
1st pass at styling release announcements index
Add Upcoming Calendar tab menu to statistics index

This is a bit hacky at the moment.  The idea is to eventually
split out statistics into it's own site section living under
/statistics, but that is too hairy a job for now.
Frontend::ReleaseAnnouncement -> StatisticalReleaseAnnouncement

(rename)
Statistics announcement rummager search faked with SQL

We'll need this for running in dev mode anyway (although we arguably
should be running rummager in dev mode too).
StatisticalReleaseAnnouncmentFilter uses times instead of dates
Bring everything more inline with rummager api

Feature now uses StatisticalReleaseAnnouncementProvider::FakeRummagerApi
instead of stubs.

FakeRummagerApi returns stuff in exactly the schema as rummager.

StatisticalReleaseAnnouncementFilter thinks in times instead of
dates and is more intelligent about them.