[core] Improve SAML configuration parameters

# Xmlsec1 binary path. This program should be executable by the user running Hue.
## xmlsec_binary=/usr/local/bin/xmlsec1

# Create users from SSO on login.
## create_users_on_login=true

# Globally unique identifier of the entity.
## entity_id=http://localhost:8888/saml2/metadata/

# Consumes assertions sent back from IdP.
## assertion_consumer_service_uri=http://localhost:8888/saml2/acs/

# Logout using the SSO provider.
## single_logout_service=http://localhost:8888/saml2/ls/

# Required attributes to ask for from IdP.
## required_attributes=uid

# Optional attributes to ask for from IdP.
## optional_attributes=true

# IdP metadata in the form of a file. This is generally an XML file containing metadata that the Identity Provider generates.
## metadata_file=

# Private key to encrypt metadata with.
## key_file=

# Signed certificate to send along with encrypted metadata.
## cert_file=

# A mapping from attributes in the response from the IdP to django user attributes.
## user_attribute_mapping={'uid':'username'}