System was using the empty state return from theme_path,
when no theme was configured, for loading in languages
which would result in the root path being looked up upon.
This changes the theme_path helper to return null in cases a theme
is not configured instead of empty string to help prevent assumed
return path will be legitimate, and to help enforce error case
handling.
For #2836
Was no longer needed due to only being there to perform
language extension for de_informal but now this is done by crowdin
instead so it's redundant. Same goes for checking and formatting
scripts.
Also removed comment advising deletion form settings.php language list
since this is now auto-copied to languages anyway.
Related to #1261
Extended the base Laravel translation system to
allow a locale to be based upon another.
Also adds functionality to take base & fallback locales into account when fetching
an array of translations.
Related to work done in #1159
