.module: Remove subscription (and mail_edit) code which has been moved to pm_subscriptions.
.info: Remove dependency on subscriptions and mail_edit modules.
.install: Remove mail_edit queries. Roll back user table alteration. Roll back triggers update.

#182369: Add variables column in _install; Add update.

As this is a development branch, no rollback update path will be provided for testers. See issues in question for more information.

*DB upgrade*