Links create sometimes undocumented attributes

[rettigl]

In cases where e.g. an NXtransformation axis is linked with an NXdata axis on the hdf5 level, this creates on each side undocumented attributes (attributes of NXtransfomation/AXISNAME are not the same as NXdata/AXISNAME field). In addition, the linking mechanism creates a "reference" attribute, which is also not documented. How do we deal with this?

• We don't care
• We avoid hdf-level links in such cases, and copy the data
• We add exceptions for the read_nexus for these cases

Please add your opinion here.