How to normalize species information

[janssenhenning]

We need to preserve the species information in get_structuredata and get_parameterdata to be able to make roundtrips via the inpgen possible, since we always need the id.

Therefore we need to normalize the species name to the format 'name-id', since the input parameters and StructureData need to keep this information independently

There are currently two different approaches used in fleur and get_parameterdata

fleur/inpgen uses id=index of occurence of the species if not specified (Though I don't know if this holds under all circumstances)
get_parameterdata uses id=index of occurrence of species with the given element

The second approach is more natural in my opinion but this means renaming more species coming from fleur directly.
Another approach is to not change the species name if it corresponds to the valid format and only change the ones not conforming like the default names Iron (Fe). There we have to be careful not to double the species names