Add ElectronicDOS and XASSpectra properties

[JosePizarro3]

@ndaelman-hu

We have to add the ElectronicDOS and XASSpectra base class with the same functionalities as in the normalizers. Important links to the old schema:

Calculation old schema
Band structure normalizer
DOS normalizer
Spectra normalizer

[JosePizarro3]

Some thoughts on the DOS schema:

• Merge DOS and Spectra into a base class named ElectronicSpectralProfile. I think it makes sense to define and even more upper-level class called SpectralProfile, thus ElectronicSpectralProfile(SpectralProfile) and all the properties will be ElectronicDensityOfStates(ElectronicSpectralProfile), XASSpectra(ElectronicSpectralProfile), EELSSpectra(ElectronicSpectralProfile), and so on. One example for a non-electronic spectral profile would be XRDPattern(SpectralProfile).
• Define projected-DOS using refs to AtomsState/OrbitalsState.
• Store max value, normalization factors, integrated values.