allow using queryParam to disable filter

much better than global state (and should potentially replace cookie usage that is user controlled)

src/Extensions/GroupSubsites.php

@@ -153,6 +153,9 @@ class GroupSubsites extends DataExtension implements PermissionProvider
         if (Cookie::get('noSubsiteFilter') == 'true') {
             return;
         }
+        if ($dataQuery && $dataQuery->getQueryParam('Subsite.filter') === false) {
+            return;
+        }
 
         // If you're querying by ID, ignore the sub-site - this is a bit ugly...
         if (!$query->filtersOnID()) {