Crowdin

This branch contains all relevant string.xml-files for the Crowdin-translations. I've not added the .yaml-config-file as it contains our API-key as discussed with @stypen 
Maybe we can also integrate crowdin later with gradle.

ongoing testrun: https://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/1150/
Should be ok - only strings added ;)