Avoid saving new translations that are empty, remove existing empty translations. 

Activeadmin-globalize3 renders inputs for all possible translations. Consequently, `params` will contain translations for all attributes - even empty ones - and many empty translation records will be created.

This feature registers a `before_filter` in `ActionController::Base` that will

1. remove new and empty translations from `params` before creating any empty records
2. mark existing and empty translations in `params` for deletion

See https://github.com/stefanoverna/activeadmin-globalize3/issues/10, most credits go to [codingluke](https://github.com/codingluke) and [fabn](https://github.com/fabn), thanks!