Backups: Support for general data (users, jobs, cache)

[ChristianGruen]

Commands and XQuery functions for creating, deleting, altering, restoring and listing backups should be extended for handling general data (users, jobs, caches):

• General data can be addressed by supplying an empty string to db:create-backup(), db:drop-backup(), db:restore() anddb:backups(), or by omitting the database argument for CREATE BACKUP, DROP BACKUP and RESTORE.
• A timestamp can be attached to address a specific backup.
• The DBA needs to be enhanced to list general backups.

[ChristianGruen]

Documentation:

• https://docs.basex.org/wiki/Database_Module#Backups
• https://docs.basex.org/wiki/Commands#Backups