slapos_jio_ui_test: implement multi-language test with getDefaultAvailableLanguage() and Base_translateString()

   When a Hosting Subscription is destroyed, the related Subscription Request is stopped.

   This can prevent a useless message be pushed to the user.

   By replacing the templates, the site must indeed continue to work as usual, and the new organisation should take place of organisation_module/slapos

     Create methods to replace the templates on preferences by their clones with small modifications.

    The goal is allow us to ensure that the values on the templates aren't harcoded on other locations, making it impossible to reconfigure the site.

   Move definition into preferences

    Merged into SystemPreference_viewSlapOS Form

    The source was changes to be same as source_section

See merge request nexedi/slapos.core!222

See merge request nexedi/slapos.core!240

This reverts commit 7e49ec5e.

This reverts commit febcf1b4.

See merge request nexedi/slapos.core!239

See merge request nexedi/slapos.core!185

See merge request nexedi/slapos.core!236