App namespace in stubs

[mrterryh]

When generating a file, the stubs assume the App\ namespace. This should be replaced with the app name in case the user changed it with php artisan app:name

[mrterryh]

For an example on how this can be achieved, refer to this: https://github.com/laravel/framework/blob/8865d2276be94f0a3497ba3bd26c906ae9e91e1c/src/Illuminate/Console/AppNamespaceDetectorTrait.php