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.
Statistical release announcements paginate

• FakeRummager's schema now identical to rummager including the total result count.
• Results are handed back in a CollectionPage with extra pagination metadata.
• Results are consumed through the filter object instead of being assigned by the controller.
Statistical release announcements come from rummager
Normalize styling between publications index and statistical release announcement index
Stats announcements filter uses root-level params

Because this makes better urls and is consistent with document filter.
Stats announcements can be filtered by orgs and topics
Stats release announcements filterable by topic / org
Announcement filter thinks in dates and is described