Add shibboleth discovery service

docker/shibboleth-ds/LICENSE.txt

docker/shibboleth-ds/Makefile

docker/shibboleth-ds/README.txt

docker/shibboleth-ds/RELEASE-NOTES.txt

docker/shibboleth-ds/blank.gif

docker/shibboleth-ds/idpselect.css

docker/shibboleth-ds/idpselect.js

docker/shibboleth-ds/idpselect_config.js

docker/shibboleth-ds/index.html

docker/shibboleth-ds/nonminimised/idpselect.js

docker/shibboleth-ds/nonminimised/idpselect_config.js

docker/shibboleth-ds/nonminimised/idpselect_languages.js

docker/shibboleth-ds/nonminimised/json2.js

docker/shibboleth-ds/nonminimised/typeahead.js

docker/shibboleth-ds/shibboleth-ds.conf

docker/shibboleth-ds/shibboleth-embedded-ds.spec