FEATURE: crypto-request for SSKR

I'd like to see the ability for Gordian SeedTool to be able to request an SSKR.

four forms:

* request an initial share of any SSKR.
* request a specific SSKR identifier., or list of SSKR identifiers (possibly animated)
* response of an SSKR, or list of SSKRs.
* (optional) request a specific group and return any SSKR within that group (is there a group identifier?)

Initial user-facing features would be:

*Each SSKR printed cover page would have a crypto-request for its issued QRS.

* Scan an initial SSKR share and SeedTool will request additional SSKRs with a QR crypto-request displayed in its UX, as well as accept a scan of another SSKR even if not from a crypto-response, and warn if it is not part of the set.

* (optional) store SSKR identifiers issued with master seed and master public key info,

The ideal is that if someone has an offline copy of the SSKR cover sheet, they can initiate the process to restore the seed.

I recognize there are state and metadata dependencies in SeedTool that likely have to be implemented first, and it is likely that we should do crypto-envelope first.