LIBCLOUD-450: Update GCE to v1

Update GCE to v1.
The primary change for v1 from v1beta16 is that ephemeral disks have gone away and now all disks are persistent.  This means that create_node is now creating a disk first if an existing disk isn't supplied.
Also, add support for snapshots.

This is obviously a fairly large change, although most of the actual changed lines are for test fixtures.  Now that v1 has launched, the treadmill of releases with large changes should slow down to a more reasonable pace.