Volumn-level Mapping Works Only Circumstantially for Phases and CourseSummaries

[Dtphelan1]

The dose-to-volume sub-tables in phase and course summary sections are fragile. They only work because the data we parse happens to align BodySite indexes with codexrt-radiotherapy-dose-XX-to-volume extension indexes, where XX is planned or delivered; this, AFAIK, is not a requirement of the IG and can collapse whenever. Ideally, we would be using information on the codexrt-radiotherapy-dose-XX-to-volume's volume extension, using its valueReference to get display information.

For the purposes of a quick proof of concept, this is sufficient, but should be fixed long term.