Query with language (admin)

[xipasduarte]

The admin should work to allow for improved simplicity, but there is a special mode that is specific: all languages.

Things to consider:

• A user can have a default language different from the site's default language. However, this language is selected in the profile from all available languages for the interface (language packs), so the choice needs to be checked.
• If the user's interface language doesn't exist the site's default language is used.
• Users an change the language in the switcher and that is carried while they keep the session (cookie based).
• Language should follow the order of priority: current, user default, site default.
• Content should be filtered according to the language that has the highest priority.