C2MS12 — Add a section describing expected use

There is frequently confusion about how C2MS should be used. Normal use patterns are not described in the C2MS document, and this would be useful to add as a guide to users. This is especially true when C2MS is used in an enterprise environment, because common interpretation is critical.

The idea is to communicate context for how C2MS has been created and how it is expected to be used.

This could be in the form of a section called "System Architecture", "Guidance", "User Guide", or something like that.