added 'knife hp volume list' command.

Hi,

I added 'knife hp volume list' sub command.

<pre>
$ knife hp volume list
Name         ID                                    Size  Availability_Zone  Status
fogvolume01  50f4adfd-45ab-4956-96b1-4831a19c90f2  1     az3                available
</pre>

Thanks from Sunny Tokyo :dash: