Updated documentation about hidden enforce_external_nicknames feature, and about CFG_ACCESS_CONTROL_LEVEL_ACCOUNTS behaviour with external logins.
Updated documentation about hidden enforce_external_nicknames feature, and
about CFG_ACCESS_CONTROL_LEVEL_ACCOUNTS behaviour with external logins.

tiborsimko/invenio-access,inveniosoftware/invenio-access,tiborsimko/invenio-access,inveniosoftware/invenio-access