cli: auto-detect metadata file or block device
cli: auto-detect metadata file or block device

If it's a file, assume it's in XML format already.
If it's a block device, assume it's in the binary encoding and
  use Thin.dump.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

djs55/thin-cluster