Add internal.py actorkeys dict

There are a handful of FITS cards which are added manually (well, by code instead of directly from external actor dicts). We need to provide a list of these and their formats, etc. to NAOJ. So add an internal.py dictionary to hold the definitions. I do not expect to fill in values and to use the actorkeys-to-FITS mechanism to generate the FITS cards, mostly because we have no way to order/group such cards in the headers.