Fix support for SOGoSieveFolderEncoding defaults

Fixed the following bugs in the mail filter editor:

1. Sieve folder encoding not respecting the SOGoSieveFolderEncoding
system defaults;
2. Conditions are still displayed when rule affects all messages;
3. Missing custom mail labels to "flag with" action.

UI/Templates/PreferencesUI/UIxPreferences.wox

@@ -21,6 +21,7 @@
     var defaultEmailAddresses = '<var:string value="defaultEmailAddresses" const:escapeHTML="NO"/>';
     var forwardConstraints = <var:string value="forwardConstraints" const:escapeHTML="NO"/>;
     var sieveCapabilities = <var:string value="sieveCapabilities" const:escapeHTML="NO"/>;
+    var sieveFolderEncoding = <var:string value="sieveFolderEncoding.doubleQuotedString"/>;
   </script>
 
   <script type="text/ng-template" id="preferences.html">