Geometry recipe improvements

[zjttoefs]

8CB1EBAE3B2DA51D has lazy validation. In process() it only checks that geometry groups exist and that they are valid. No checks are done if the depends_on chain is there and checks out. There is some duplication between the simple verification code and the one that runs when running the full OFF building (hdf visitor).

Also: The title is too long and the NeXusOFF as no meaningful repr or str method. So the output from the processing of the recipe is not helpful.