Add a script to copy translations into our git repo

We want to have the translations as part of our git repo for the following reasons:

• developers should build with translations so it is possible to debug translation issues
• nightly builds should have translations
• a build should not fetch stuff over the network, so we cannot fetch the translations dynamically
• tagging a new version creates a release on gitlab, which should include translations, instead us downloading the tarball and adding translations manually

This script simply checks whether we're in master or not, and fetches the corresponding translations using the svn command.

The script is meant to run nightly, like scripty.

Note: this doesn't automatically commit the translations yet, that's still a manual step until I'm confident enough.

CCMAIL:kimageshop@kde.org