Feeds support for all entities, and entity languages

As per issue https://www.drupal.org/project/weight/issues/2844849 💬 Does this module work with Feeds? Fixed , Weight now offers feeds support for weight fields, but only for node entities.

It'd be great to extend this support to all entities.

Additionally, the patch in the issue above hard-coded LANGUAGE_NONE when assigning the value to the weight field. As per the example provided in feeds.api.php, it's possible for the callback to use the language column of the entity when assigning the value weight field array.