Patch managesieve for SSO login

See issue #2 for details. This is a temporary solution.

patches/managesieve-sso.patch

+diff -urN old/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php new/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php
+--- old/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php	2019-01-17 17:16:48.444068789 +0000
++++ new/plugins/managesieve/lib/Roundcube/rcube_sieve_engine.php	2019-01-17 17:18:03.692742949 +0000
+@@ -93,7 +93,8 @@
+         ));
+ 
+         // connect to managesieve server
+-        $error = $this->connect($_SESSION['username'], $this->rc->decrypt($_SESSION['password']));
++	// A/I patch: fetch the SSO token from the Apache request environment.
++        $error = $this->connect($_SESSION['username'], $_SERVER['SSO_TICKET']);
+ 
+         // load current/active script
+         if (!$error) {