Update the git-archive export options

The .gitattributes, .gitignore, .commit-template files do not need to be
present in packaged sources, as they are for people using the Git
repository.  People who download tarballs usually don't reimport into
Git -- they should just download the actual repositories.

Change-Id: I04d2ca436f5174c7820b42b6f5b2b9648c925fe3
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I1a43928ab6b5c1458c1f662896e022b24bf38ee1