More flexibility in Kind names, at least should not fail.

[broeder-j]

Currently, a structure with a Kind name of 'Iron (Fe)' will cause the inpgen plugin to fail, since it fails to set kind_namet but this failure is not caught.

"""
Error: kind_namet is referenced before assignment
"""

If we do not allow kind names like this (through this was created somewhere per default), there should be no internal error, but a clear error message.

Add on this new naming was introduced in with the new inpgen implementation of Fleur > MaX 5.0.