Renames relative_molecular_mass

[mtwharmby]

relative_molecular_mass was carried over from the contributed
definition NXcontainer. For consistency with the chemical_formula field
and also with (e.g.) the CIF definitions, it should be renamed
chemical_formula_weight.

This was discussed (some time ago) with @markbasham

Signed-off-by: Michael Wharmby [email protected]

[prjemian]

Added to 2017-07-25 telco that this PR will be merged unless there are objections raised.

[zjttoefs]

relative_molecular_mass is the historical NeXus term and I see no reason to change that by the way of a pull request, especially since the field was only re-confirmed in NXsample_component last October.

[mtwharmby]

Rather than closing, might it not be worth discussing?
As a reason to change the name: consistency with other fields in NeXus (e.g. chemical_formula) and also with CIF format. Also by having similar names, when looking at the NeXus tree, chemical_formula and chemical_formula_mass/weight appear together, which helps readability.

Also, the last time I heard anyone use the term relative_molecular_mass was in a high school science text book (though searching the web, hit number five on Google is the IUPAC gold book)