Revocation section update

[rogulati]

trafficstars

Update to revocation section

[quartzjer]

@rogulati Is this ready for review? Most of the json-tagged markdown sections contain invalid JSON yet :)

[dwight-holman]

Most of the included language and steps are also given in the referenced standards. The bits that aren't seem to be included in the examples, which are non-normative. If this was intended to address #22 , we need information about the message type and request headers (which are absent from the id-hub standard, but necessary to resolve revocation)