MBS-4115, Schema changes for .png/.gif support.
Merge remote-tracking branch 'origin/schema-changes-2013-05-15' into mbs-4115

* origin/schema-changes-2013-05-15: (482 commits)
  Precedence of && is higher than //, so edit medium wasn't grouping the comparison correctly.
  MBS-4419, freeze/thaw things Catalyst wants to store in a session.
  Update carton.lock.
  Quick temporary instructions for recent carton versions.
  Update translations from transifex.
  Recompress all the images, for slight gain.
  Update languages from transifex.
  MBS-5960: url-escape more things Ian forgot in writing the wikipedia extract code
  MBS-5956: stop comparing undef as a number in Edit Medium
  Update instruments.pot partway -- only add new instruments.
  Update the .pot files that don't require migration scripts.
  MBS-5954 Confirm revoking OAuth access
  Do not compare with $args->{fmt} if it is not initialized.
  Turn MusicBrainz::DataStore into a role and remove dead code from it.
  MBS-5955: HTML::FormHandler, cursed be its name, won't allow localize_meth while overloading a field definition
  Fix tests: add missing comma in Form::Merge
  Update .po files from transifex.
  Update .pot files.
  MBS-5945 Do not silently fail when there is an invalid URI in the input, but the user switched to "Installed Application"
  Allow any HTTP or HTTPS URL (e.g. localhost is OK, FTP is not OK)
  ...
MBS-4115, use mime_type as primary key for image_type, simplify update script.
MBS-4115, rename cover_art.image_type column to mime_type.  Update upgrade.sh.
MBS-4115, Fix cover art archive replication triggers.
MBS-4115, updates based on code review feedback.

- add cover art image types table to import/export scripts.
- move foreign key creation to a seperate script, as it should not run on slaves.
- fix incorrect column name in foreign key creation.
MBS-4115, move foreign keys to the correct place in upgrade.sh
Merge remote-tracking branch 'origin/schema-changes-2013-05-15' into mbs-4115

* origin/schema-changes-2013-05-15:
  MBS-4756/MBS-5918: use ocharles' suggestion for loading index from DB cleaner
  MBS-4756/MBS-5918: add transclusion table migration to upgrade.sh
  MBS-4756/MBS-5918: corrections to index migration code recommended by ocharles, plus documentation of race condition
  Trying to stop it conflicting. Again.
  Trying to get this to merge
  Add the stuff to upgrade.sh
  Add the upgrade.sh stuff
  Remove carton.lock from diff
  MBS-4756/MBS-5918: create a migration script reading in the old disk-based transclusion table and inserting into the DB
  MBS-4756/MBS-5918: update tests to reflect new wikidocs system in DB
  MBS-4756/MBS-5918: transclusion -> DB, main UI fixes. tests and migration script needed still
  Make sure to properly drop and recreate replication triggers in upgrade.sh
  Preparing schema change branch for 2013-05-15
  Removing unused preview bit
  Adding descriptions to collections

Conflicts:
	upgrade.sh
Merge branch 'mbs-4115' into schema-changes-2013-05-15

* mbs-4115:
  MBS-4115, move foreign keys to the correct place in upgrade.sh
  MBS-4115, updates based on code review feedback.
  MBS-4115, Fix cover art archive replication triggers.
  MBS-4115, rename cover_art.image_type column to mime_type.  Update upgrade.sh.
  MBS-4115, use mime_type as primary key for image_type, simplify update script.
  MBS-4115, Schema changes for .png/.gif support.

Conflicts:
	upgrade.sh