create ICD-9 code ranges, optionally including parents which have broader scope.

[jackwasey]

include parent codes even if not all child codes are to be included in the range requested.

E.g. "V10.09"" to "V10.11" would not normally include "V10.1"

This may be useful, since people use ICD-9 ranges in many publications, and seem to have slightly different meanings, including the possibility described above. The current implementation is the most conservative in not including codes which could imply additional codes than those specified in a range.

[jackwasey]

Nobody seems to care about this, and I don't. If it transpires that a comorbidity parsing error arises from this subtlety, I'll reopen.