Multilanguage: editing associated items. Thanks  Dennis Hermatski

This patch lets edit associated items right from the administrator edit item page => Associatons Tab for contacts, categories, articles, newsfeeds.
It loads the associated item in a modal where changes can be done and saved.

The patch adds a modal field type for categories and modifies the modal field types for the other components, at the same time normalising them for contacts and newsfeeds.

These modals can now be used by any 3pd.