Accept PQ units with m^2 by replacing them with m2.

This is a workaround, until either PQ supports m^2 notation, or the generated
documents do not contain these codes anymore.
Add local terminology mapping to SNOMED-CT.

This is an ad-hoc method that consists of a simple table with the mapping,
currently only some of the Portavita local codes to SNOMED-CT.  Can be replaced
with a method that queries a central terminology service.