add SWIFT (openstack object storage) storage backend

3rdparty/php-cloudfiles/.gitignore

3rdparty/php-cloudfiles/AUTHORS

3rdparty/php-cloudfiles/COPYING

3rdparty/php-cloudfiles/Changelog

3rdparty/php-cloudfiles/README

3rdparty/php-cloudfiles/cloudfiles.php

3rdparty/php-cloudfiles/cloudfiles_exceptions.php

3rdparty/php-cloudfiles/cloudfiles_http.php

apps/files_external/appinfo/app.php

apps/files_external/lib/swift.php

apps/files_external/tests/config.php

apps/files_external/tests/swift.php