Clarify link between service and command

Situation: there is no clear relationship between concepts switchOnService and OnCommand, although their name suggests there is. There is nothing specific about “On” in the description.

Proposal: Clarify/document the relationships between services, functions and commands in the documentation.Explain the link is in oneM2M.

Status: agreed during SmartM2M-2nd RG Meeting about 2 NWIs SAREFv3 and SAREF Com Framework V2 2019-05-06. Open question: keep service in SAREF, or just import oneM2M , or just reuse a subset of oneM2M terms, without importing it ?