AF and AT: consistent localization/translation system

[rschweigert]

implement a simple mechanism for localization/translation of AF and AT-Backend

Currently, localizing the framework plugins and extensions is a quite messy task. You have to translate dozens of files spread over the whole filesystem and with many repetitions. Even worse is the situation in AT. Here are some backend labels still hardcoded and difficult to find.

It would be nice, if there were a centralized localization system for both, AF and AT.

My suggestion is to use XLIFF (XML Localization Interchange File Format).

Further readings at:
https://en.wikipedia.org/wiki/XLIFF
https://libraries.io/search?keywords=xliff&languages=JavaScript