Add support for optional specialization

[kirkeugle]

Rules state that optional specialization decrease difficulty and add an additional -2 to defaults from the specialized version of that skill. Things you currently have to adjust manually. (Specialities, B169+)

[richardwilkes]

This is an issue for the data files, not GCS. No one (to date) has cared enough to do the necessary data entry and submit the result for inclusion.

I'll move this over to the GCS Master Library repo and perhaps someone (or you!) will be interested enough to make the necessary effort.