redo Background and Context section

• remove summarizing list since can be found in resource itself ( move any notes or comments not into description details if needed)

• move last sentence to Scope and Usage section adn change from "Typically, an observation will have either a value or component observations, and not both. " to "Normally, an observation will have either a value (e.g. a blood glucose measurement) or a set of related observations ( e.g. an electrolyte panel) and not both. A few observations (e.g. apgar store) may have both a value and related observations (for apgar, the observations from which the measure is derived)."