VCTF Use Cases update

As we discussed briefly in the call today, we are gaining traction on the
use cases document.  Gregg, Brian, Daniel, and I will be working on it
going forward.

The general approach I have taken to get this rolling is:

   1. Start from the CCG use case document at [1]
   2. Restructure to be more like the Web Payments Working Group use cases
   document at [2]
   3. Organize around the major operations that can be peformed on / with a
   Verifiable Claim.
   4. Extract core requirements with associated use cases from the CCG
   Google Doc use case document [3] and the CCG anonymized use cases that came
   in from the industry survey as reflected at [4]
   5. In parallel, write up a *simple* illustration of a basic flow for a
   Verifiable Claim in the wild that we can use as an introduction to the
   concepts.

There is still a lot of work to do here.  I will be coordinating closely
with the other volunteer editors. We are operating on github, using
branches and pull requests.  Feel free to observe, comment, or assist!

[1] http://www.opencreds.org/specs/source/use-cases
[2] https://www.w3.org/TR/web-payments-use-cases/
[3]
https://docs.google.com/document/d/1GySrTXAYpwa4vDPsGE3BMA42FwIAqAyLGigKuKUTGks/edit#
[4] http://opencreds.org/presentations/2015/w3c-tpac/anonymized.html
-- 
-Shane