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: I34c049b99475c2aee448a075dec30e5471bf8f83
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>

.gitattributes

@@ -1,3 +1,4 @@
-.tag            export-subst
-.gitignore      export-ignore
-.gitattributes  export-ignore
+.tag                    export-subst
+.gitignore              export-ignore
+.gitattributes          export-ignore
+.commit-template        export-ignore