Formal Equivalence w/ CQL and UCUM durations

Agreed, add discussion of quantity equality, equivalence, and comparison with respect to calendar and definite quantity duration units to the Appendix B reference documentation. In addition, in the Quantity discussion, and the unit conversion discussions, make clear that definite quantity unit conversion follows UCUM conversion, and calendar duration conversion is performed as: 1000 milliseconds = 1 second 60 seconds = 1 minute 60 minutes = 1 hour 24 hours = 1 day 12 months = 1 year Note specifically that unit conversion between (years and months) and (days or below) is not defined.