qt: remove de_AT translation

Got too many complaints that is was unserious and written by trolls.
I have also removed the translation from transifex.
Fixes #4054 and #3918.
VERSION obtained from source instead of the previous git tag.

Drawback: The version string is no longer a valid git identifier.
          For this reason the 'g' short hash prefix has been removed.

Exception: When building directly from a tag this behaves exactly like the previous behavior.
           This allows formatting release versions with precision     i.e. v0.9.2
           This also allows arbitrary topicbranch names               i.e. v0.9.1-glibc-compat