Switch po file translations from bzr to git, needs manual removal of /data/locale/website directory.

This merge request switches the po file translation repo from launchpad to gitlab. Additionally, it improves the visibility of original po file authors, for those cases where the author was named explicitly when committing.

When merged, and applied to live branch (or any existing branch), it will require deletion of the /data/locale/website folder to work properly. As this is a one-time transition, we could get away with informing contributors about the change, instead of checking if .bzr exists, and then deleting the directory.

If you prefer, however, I can add that little deletion part, too, before the merge.

Also, I would like to know how to handle the settings for the translation repo first, before this is applied to the live server. Sylvain hinted at the possibility of 'just anyone' currently being allowed to push to that repo (which still needs to be confirmed by testing, see inkscape-web-i18n!1 (merged)).