Allow different language types to be enabled separately

fixed a simpletest

slightly reworked patch

@alexanderpas: thanks for the review, this patch was created as part of a proof of concept work so initially I did not provide any specific test. In the current one the new functionalities have their own tests (I discovered a bug thanks to them :).

rerolled

I forgot to fix my own tests :(

Straight reroll.

my own tests...
(sigh)

A couple of screenshots to help people understanding what's going on here.

How do you imagine other language types would work with this?

I ain't sure this feature request still makes sense, I postponed this issue after the language negotiation revamp to see if this was still needed or useful. If we want to go on this way, I'd simply change the radios in a multiple checkbox selection listing all the available (configurable?) language types.

Are you thinking about introducing an admin language type? It might be tricky, I'd just go with smart language detection methods (see the second example in http://drupal.org/update/modules/6/7#language_negotiation), after all we are setting UI language here not else.

I agree that they are not ideal, I just meant that we can already achieve something similar with what we have in D7 core. IMO the best approach would be to have an admin language detection method that checks if the current page is an admin page and return a configured value or FALSE otherwise.

Unless perhaps we want to make admin language type non configurable, so it won't appear in the configuration page. But I think that page needs some usability improvement anyway.

Not working on this currently :)

More lively discussion at #1314250: Allow filtering/configuration of which languages apply to what (UI, nodes, files, etc).