fix(install): add created superadmin to most powerful group in instance, ie. superadmin

        $user = new User($data);

        $userModel->save($user);

        $user = $userModel->findById($userModel->getInsertID());

        // set newly created user as most powerful instance group (superadmin)

        $user->addGroup(setting('AuthGroups.mostPowerfulGroup'));

        $this->write('Super admin "' . $username . '" created', 'green');

    }