Feature: Allow to pass assertionId as query parameter to the revocationList request

[raiseandfall]

Describe the feature

The OpenBadges 2.0 spec defines revocationList as a list of revokedAssertions. This list can potentially become enormous as the list ofrevokedAssertions grows.
We want to be able to pass the assertionId as optional parameter to the request, so the server returning the list of revoked assertions can filter on its end, reducing the response payload size & load time. This will also help server side scripts who deal with list max count (i.e. returning only the first 100 items).

We propose the following URL format:
{revocationList}{?|&}assertionId={assertionIdValue}

Per OpenBadges 2.0 spec, the response shape of the request should not changed.