ADD: theme version in frontend config.

Author: ivan-nginx

layout/_partials/head.swig

@@ -114,6 +114,7 @@
   var CONFIG = {
     root: '{{ theme.root }}',
     scheme: '{{ theme.scheme }}',
+    version: '{{ theme.version }}',
     sidebar: {{ theme.sidebar | json_encode }},
     fancybox: {{ theme.fancybox }},
     tabs: {{ theme.tabs.enable }},