Correct inconsistent frequency determination in CumulativeMedicationDuration logic

[brynrhodes]

The ToDaily(Code) function in this library incorrectly uses the lower number of doses for frequencies that are specified as a range of hours:

https://github.com/cqframework/CQL-Formatting-and-Usage-Wiki/blob/master/Source/Libraries/CumulativeMedicationDurationFHIR4-1.0.000.cql#L174

In addition, add this comment to the description of the function:

Note that for ranges, the boundary resulting in the highest frequency result is used. E.g. `Every two to four hours` results in `12.0` and `One to two` times a day results in `2.0`.