URL Handling: Removed referrer-based redirect handling

Swapped back handling to instead be pre-determined instead of being
based upon session/referrer which would cause inconsistent results when
referrer data was not available (redirect to app-loaded images/files).

To support, this adds a mechansism to provide a URL through request
data.

Also cleaned up some imports in code while making changes.
Closes #4656.

app/Users/Controllers/RoleController.php

@@ -154,7 +154,7 @@ class RoleController extends Controller
         } catch (PermissionsException $e) {
             $this->showErrorNotification($e->getMessage());
 
-            return redirect()->back();
+            return redirect("/settings/roles/delete/{$id}");
         }
 
         return redirect('/settings/roles');