Terminology around pinned-domain-cert

[mcr]

> 4) Terminology, around Line 233: do you need to introduce
> "pinned-domain-cert" certificate as a term?  Somewhere (perhaps earlier
> in the introduction) it might be useful to briefly introduce the
> different actors and how they relate: i.e. MASA used by the
> manufacturer of the device to sign a voucher for a pledge, which may
> indicate the owner of the device (?), the Registrar, acting for the
> network domain and deciding who may or may not join a given network,
> the Owner or Network Operator who wants to securely deploy the plege,
> etc