Added support for format="gce"

This is for creating Google Compute Engine ready images to be
uploaded into a bucket in the google cloud storage via gsutil
Fixup createGoogleComputeEngine

There are some conventions around the naming and content of
a GCE tarball. This patch hopefully addresses all of them
Fixup createGoogleComputeEngine

no paths allowed inside the tarball, only the disk.raw
they are really strict on their checks :-)
Added bundle task for GCE images
- v5.06.169 released