Add a way to explicitly revoke an identity

A possibility it to add an extrinsic like identity.del_all_rights()

added P5-sometimesoon S-ToDo labels

mentioned in issue #11 (closed)

assigned to @tuxmain

removed S-ToDo label

added S-doing label

mentioned in merge request !12 (merged)

changed milestone to %ğdev currency launch

changed milestone to %ğtest migration

closed with merge request !12 (merged)