Major: CoRE explanation under 3.1 Architecture

[mkovatsc]

Primarily, text related to Figure 4 (Thing-to-Thing communication) explaining client + server

After all this time, I think this document tries to explain, why there has been a “Constrained RESTful Environments” group in the first place and what the benefits of REST are for such an environment. This somehow is in this document, but not explained well…
Something to intro?

Need short list why Contrained REST environments / use of REST is a good idea. Anarchic environment where everyone can put their stuff and link together with hypermedia. Compared to MQTT broker where everyone needs to agree on topics etc.

[mkovatsc]

Also give context for 3.2. System Design -- resource state and

the client state must be kept only on clients

Maybe say that the whole design assumes that a server can have multiple clients that (by default) interact through the server.