keep language settings active over module updates

I'm thinking of creating a fluidui_translations directory in the Drupal public directory (sites/default/files) when installing the module, to store the translatiosn and the table of contents there, and add another field in the config settings page to check which translations to enable.

I think the the table of contents needs to be updated to reflect the latest infusion library changes, I'll have to check that too.

In progress...

Sadly, the documentation for localization support is very bad: https://docs.fluidproject.org/infusion/development/LocalizationInThePref...

I was able to setup multiligual settings in the toolbox, and not to lose the translations after the module is upgraded, in the README.md you will see a procedure on how to do that, I'll leave the task to "Needs Review" for now.

No testers, ok, I'll merge to the 3.0.x branch and make a DEV release, this one is still very experimental so I won't create a tagged release out of this. I'll also mark this as "Fixed" for now, but I'll investigate more to see if I can avoid the manual step that I outlined in the README.md file