Fixed LIB robot user/cert migration.

Added guardian migration for LIB user pipeline perms.

Corrected LIB username.

Fixed translator.py to read JSON for LIB events.

Needed to freeze gracedb for guardian migration.

Changes for new LIB user/pipeline and permissions.

Added model level permissions on Guardian.GroupObjectPermissions for members of the executives group. Also restored a modified version of the ModelBackend that *doesn't* do authentication. This is so that the has_perm check on Models can work.

Changed migration for existing event permissions to apply defaults to *both* the Event and the event subclass instances.

Added view permission for event, created permission objects for existing events, and added code to apply default permissions when new events are created.