Display total servers user can access in the Admin CP

closes #356

app/Http/Controllers/Admin/UserController.php

@@ -44,7 +44,7 @@ class UserController extends Controller
      */
     public function index(Request $request)
     {
-        $users = User::withCount('servers');
+        $users = User::withCount('servers', 'subuserOf');
 
         if (! is_null($request->input('query'))) {
             $users->search($request->input('query'));

app/Models/User.php

@@ -239,4 +239,14 @@ class User extends Model implements AuthenticatableContract, AuthorizableContrac
     {
         return $this->hasMany(Server::class, 'owner_id');
     }
+
+    /**
+     * Return all servers that user is listed as a subuser of directly.
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\HasMany
+     */
+    public function subuserOf()
+    {
+        return $this->hasMany(Subuser::class);
+    }
 }