MBS-6058: New schema to model deleted/merged entities separately

This new schema allows us to have real foreign key constraints for active
subscriptions, as the bug in MBS-6058 occurs because HumHumXX is subscribed to
artists that don't exist (but also have apparently not been deleted).

The _deleted tables point to artist_/label_deleted rows, which collect lists of
MBIDs that have been deleted, along with the last known name/comment in order
for us to display the deletion clearly in the subscriptions. This data is
probably interesting to customers too, and has uses for us internally (better
404 pages).
MBS-6058: Rewrite deletion/merge code to use new subscription tables
MBS-6058: Rewrite Data layer to have three separate entities for subscription types

It now uses one entity class for subscriptions against entities that are still
'active' (not deleted), another for entities that have been deleted (tracking
the last known name/comment) and another for entities that have been merged.
MBS-6058: Fix subscription emailing script with the new subscriptions model
MBS-6058: Fix the email generation templates
MBS-6058: Factor out the subscribe-on-create logic into a role
Merge branch 'master' into mbs-6058

Conflicts:
	admin/sql/DropFKConstraints.sql
	admin/sql/DropPrimaryKeys.sql
	admin/sql/DropTables.sql
	lib/MusicBrainz/Server/Edit/Artist/Create.pm
	lib/MusicBrainz/Server/Edit/Label/Create.pm
MBS-6457: Do not allow created deprecated relationships in relationship editor

If the user attempts to select a deprecated relationship type, an
error will be added to the relationship type field, informing the
user that the relationship type is deprecated and the "Done" button
will be disabled until this error is corrected.
MBS-6457: Move deprecated relationship information to JSON

Adds a new 'deprecated' field to the JSON representation of the
relationship tree. This means that flagging relationships as deprecated
is now independent of the site language the user is using.
Merge branch 'master' into mbs-6058
Merge branch 'unaccent-extension'
MBS-6276: Remove padding/fix alignment of lists in edits

Removes the list bullet image and extra padding for lists inside the details of
an edit. This was requested in MBS-6276 for release events, but the fix here
affects all edit types to be consistent.
Merge branch 'mbs-6457' into beta

Conflicts:
	postgresql-musicbrainz-collate
	postgresql-musicbrainz-unaccent
Merge branch 'master' into beta