- Authority part semantics are no more prescribed; authority part has
defined syntax but reserved for future use.
- Moved away non-normative parts to "Discussion" and/or "Alternatives"
- Added `action=chat`
- Extended `via=` applicability to non-roomid cases to compensate
dropping the authority part semantics.
- Added a reference algorithm to parse a URI.
- Closed outstanding questions/discussion points.
- Added more cases for future evolution.
- Added "minimal syntax" options to the discussion of possible
alternatives
