Some recent materials about matrix parameters in DID URLs

Hello DID WG,

Since there have been some discussions in the WG about matrix parameters
in DID URLs (e.g. issue #137
<https://github.com/w3c/did-core/issues/137>), and whether they should
be used at all, I thought I'd share some recent materials:

- Slides, log, and recording from last week's DID Resolution spec weekly
meeting where we discussed matrix parameters:
https://github.com/w3c-ccg/meetings/tree/gh-pages/2020-01-16-did-resolution

- My topic paper for Rebooting-the-Web-of-Trust #10:
https://github.com/WebOfTrustInfo/rwot10-buenosaires/blob/master/topics-and-advance-readings/why-matrix-parameters.md

I hope this can provide some input for the ongoing discussion on this
topic, so we can come to consensus about the pros and cons of having
this syntax component in the DID Core spec.

Markus