Always set explicit equiv on PA summary item

It may have been lost when the item itself was written
due to fun and games depending on which side of an
explicit equivalence is written. This ensures the link
is re-established.
Merge pull request #495 from atlasapi/schedule-udpate-msg

send message on schedule block update
Stagger YouView equiv jobs

Stage and production youview jobs should be scheduled for
different times.
Stop Five updater always writing content

The updater did not merge what was already in the db, so
was always writing content, even if it was already the same.
Merge branch 'five-merge-on-write' into stage