Recognize and split out declined immunizations from regular
immunizations.

negationInd is a super important flag for immunizations, because if it
is true, the whole record is documenting that this vaccine WASN'T
administered... We were ignoring it. To avoid subjecting library users
to that same issue, we will output all declined immunizations in a
separate list called 'immunization_declines', so it will be hard to make
the same slip-up.

negationInd can exist on problems and some other sections, so we may
have to pay attention in other places. But immunizations seems like the
most likely/important usage.
Expand our reference/content parsing to deal with some data from AmazingCharts, which inserts the referenced text directly into a <td>, instead of inside a <content> tag. AmazingCharts' behavior is incorrect but seems like the kind of mistake others might make
renames 'labs' to 'results', closing #74. The labs used to have a sub-list called 'results', which I have now renamed to 'tests' because results[i].results[j] is totally incomprehensible