Merge branch 'column-width' into 'stable-3.1'

auto sidebar width (#4465)

See merge request ispconfig/ispconfig3!1050

interface/web/themes/default/assets/stylesheets/ispconfig.css

@@ -141,7 +141,9 @@ body {
 
 #sidebar {
   margin-top: 27px;
-  width: 18%;
+  min-width: 18%;
+  max-width: 21%;
+  width: auto;
   border-style: solid;
   border-width: 1px;
   border-radius: 4px; }