Merge branch 'feature/interface-cleanup'

* feature/interface-cleanup:
  Remove old SP interfaces in www/{saml2|shib13|wsfed}/sp.
  Remove backwards compatibility (related to old SP interfaces) in AuthMemCookie.
  Remove remaining references to long removed options 'enable.saml20-sp' and 'enable.shib13-sp'.
  Delete old SP metadata interfaces.
  Remove support for hosted SP metadata in MetadataStorageHandlerFlatFile.
  Remove support for hosted SP metadata in MetadataStorageHandler.
  Force XML_Shib13_AuthnRequest::createRedirect() to receive a shire.
  modules/saml: proper error message in SAML1.1/2.0 ACS when auth source ID is missing.
  docs: remove references to saml20-sp-hosted.
  docs: remove reference-sp-hosted and references to it.
  Remove code for old SP interface in frontpage/federation page.