Note:
The RDMHeader class is not currently used to formulate requests.
This may change.
Both SchemaGetter and TaxonomyGetter initialize
their RDM header strings with a correct RDM request.
Because there are other schema and taxonomy requests that can be
made which are currently not well (or not at all) documented
the standard request can be changed using setRDMHeader()
which allows you to put in anything but prevents you from changing
the request during processing (the scope of the processing
phase far exceeds the requirement for safe operation).
The setRDMHeader() method should be used with the
understanding that the interface will very likely change.
It is also possible that the constructors will change,
but the most likely scenario is that RDMHeader savvy
constructors will be added.