image_to_vm: Add vmware_raw image type
image_to_vm: Add vmware_raw image type

Allow "coreos-install -o vmware_raw" to install Container Linux with
the vmware OEM.

Use base DISK_LAYOUT to reduce the minimum disk size.

Fixes coreos/bugs#359.

coreos/scripts,glevand/coreos--scripts,coreos/scripts,glevand/coreos--scripts