Started review of SAML implementation

- Updated PHPdoc of SAML service to use type hinting instead.
- Updated groups to only sync if enabled.
- Updated names of some config props.
- Removed a couple of unused config props.
- Added exception to handle no email on SAML response.

resources/lang/en/errors.php

@@ -19,6 +19,7 @@ return [
     'ldap_cannot_connect' => 'Cannot connect to ldap server, Initial connection failed',
     'saml_already_logged_in' => 'Already logged in',
     'saml_user_not_registered' => 'The user :name is not registered and automatic registration is disabled',
+    'saml_no_email_address' => 'Could not find an email address, for this user, in the data provided by the external authentication system',
     'social_no_action_defined' => 'No action defined',
     'social_login_bad_response' => "Error received during :socialAccount login: \n:error",
     'social_account_in_use' => 'This :socialAccount account is already in use, Try logging in via the :socialAccount option.',