Add vhd-tool.0.7.0 (needs to be updated following ocaml-vhd API changes)

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #12 from djs55/vhd-tool.0.7.0

Add vhd-tool.0.7.0 (needs to be updated following ocaml-vhd API changes)