MBS-3663: extend expiration of edits that receive 'No' votes, and give editors time to respond in the case of unanimous 'No' votes
MBS-3663: slightly more efficient query for non-no-voted edits
MBS-2782/MBS-2848: don't expand (in Add Medium) or show (in Edit Medium) artist credits where all changes are visible; also, condense and visually separate expanded display
MBS-6101, Guard session lookups with a `defined $c->sessionid` check.

Any get/set on the session store ($c->session) will create the session
if it doesn't exist, which then means that particular request can now
only be serviced if the session store is available.

But a get lookup ($c->session->{somekey}) will always fail if a new
session is created for it (the new session is obviously empty), so
guard it by first checking if there is an existing session (defined
$c->sessionid).
MBS-6101, guard c.session.tport appropriately (see previous commit).
MBS-3663: remove previous-version cruft
MBS-6101: Refactor out `try_get_session`

This attempts to get something from the session, but only if a session is
already open.
Merge remote-tracking branch 'ocharles/mbs-6101' into mbs-6101

* ocharles/mbs-6101:
  MBS-6101: Refactor out `try_get_session`
MBS-6101, make Redis connection lazy.
Merge branch 'beta' into mbs-3663-no-vote-extension
Merge branch 'beta' into mbs-3663-no-vote-extension
Add cleanup and validation for soundtrackcollector
Add a test for cleanup
MBS-5524: fix up display_data to always return link_type
MBS-6296: don't show non-functional alias editing links for non-location-editors (or logged-out users)
MBS-6296: inline the disallow_editing logic
MBS-6352 Implement `./admin/ExportAllTables --check-completeness` and add more missing tables
MBS-6395, fix medium_index table.

The 2013-05-15 schema change release did not call
DurationLookup->update() in all places it should have.  Additionally a
bug was present in DurationLookup->update which prevented medium_index
rows from being deleted when they should have been.

This script fixes all those rows which could have been affected by
these bugs.
MBS-6395, add shell script to loop over update-medium-index.pl until all work is done.
MBS-6395, discs where not all tracks have a length should not have an entry in medium_index.

Incorrectly assumed sum(track.length) would be falsy if one ore more
tracks would have a NULL length.