Includes:
- docs for new realm type "saml"
- docs for new settings for SAML realms
- a guide for setting up SAML accross ES + Kibana
Original commit: elastic/x-pack-elasticsearch@85f8f6d409
* [DOCS] Move security APIs to Elasticsearch Ref
* [DOCS] Update links to security APIs
* [DOCS] Fix link to security APIs
Original commit: elastic/x-pack-elasticsearch@d7a9d3f1ab