Merge pull request #20702 from owncloud/move-user-principal-into-subfolder

apps/dav/command/createaddressbook.php

apps/dav/command/createcalendar.php

apps/dav/lib/connector/sabre/auth.php

apps/dav/lib/connector/sabre/principal.php

apps/dav/lib/rootcollection.php

apps/dav/lib/server.php

apps/dav/tests/travis/caldavtest/config/serverinfo.xml

apps/dav/tests/unit/connector/sabre/auth.php

apps/dav/tests/unit/connector/sabre/principal.php

lib/private/user/user.php

lib/public/iuser.php

tests/lib/contacts/localadressbook.php