Merge branch '6.3' into es-6.3.0

index.js

lib/auth/types/basicauth/BasicAuth.js

lib/auth/types/openid/OpenId.js

lib/auth/types/proxycache/ProxyCache.js

lib/auth/types/proxycache/parse_login_endpoint.js

lib/auth/types/proxycache/routes.js

lib/auth/types/saml/routes.js

lib/backend/searchguard.js

lib/multitenancy/headers.js

lib/multitenancy/routes.js

package.json

pom.xml

public/apps/customerror/errormessage_types.js

public/apps/login/login.html

public/chrome/readonly/enable_readonly.js

public/chrome/readonly/readonly.less

public/customizations/enable_customizations.js

public/services/access_control.js