add the block volume-options command

[caberos]

#issue1673

[allmightyspiff]

Thanks for adding this feature, I was just thinking we needed something like it :)

1. All these size/iops values need to come from the API. I think the STORAGE_AS_A_SERVICE_STAAS package has all the needed details. I dont want any of these values to be hard coded if we can avoid it, since different accounts have different options sometimes.
2. Datacenters should be its own table, like slcli vs create-options with the "closing soon" remarks.
3. "IOPS" table doesn't need a size row since those are already in the column headers.
4. That knowledgelayer.softlayer.com link doesn't work (that domain is dead).

(these can be handled in new issues)
6. A --prices flag would be a good addition
7. If possible, flag "next generation" datacenters somehow? . I know some Datacenters allow encryption at rest, which is important to indicate. https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-selectDC Like these 2 with the star on the order page.