Falocalrepo-database

* Add `JOURNALS` table and `JOURNALS` field in `USERS` table.

* `EXTRAS` field in `USERS` table is changed to `MENTIONS`, and `extras` and `Extras` folders are renamed to `mentions`
and `mentions_all` respectively.

* Information from the database are copied over to the new version, but otherwise remain unaltered save for a few
changed column names in the `SUBMISSIONS` and `USERS` tables
* Files are moved to the new structure, and the old files' folder is deleted. Only submissions files are kept
starting from version 3.0.0.