RWoT topic - Blockcerts and OBI signature alignment

Hi all,
I added a RWoT topic proposal for aligning Blockcerts/OBI signatures with
JSON-LD signatures (and/or JWS formats being discussed). This paper calls
out areas where the JSON-LD signature format has not been an ideal match
for blockchain-issued credentials.

https://github.com/blockchain-certificates/rebooting-the-web-of-trust-spring2017/blob/master/topics-and-advance-readings/BlockcertsAlignment.md

It might make sense to roll this into the existing Signature Format
Alignment topic, in which case the Blockcerts scenario can serve as a case
study.

Looking forward to RWoT!
- Kim