Data class for spectra

[ezpzbz]

When we are dealing with frequency, uv-vis, and emission spectra calculations, we generate files with arrays of numeric data which can later be used for visualization.
I need to check ArrayData, BandsData, and TrajectoryData from aiida.orm to learn more about the structure of these Data types and possibly write a new one with the export possibility for these types of data that we are dealing with in orca and also gaussian. It can be called SpectraData, for instance.
Useful starting points:

• https://aiida.readthedocs.io/projects/aiida-core/en/latest/working/data.html#working-data-creating-new-types

[danielhollas]

I am actually going to need this in a very near future. At first I think I will be developing this locally within my workflow, but am happy to contribute it here. Not sure whether custom data types belong in this plugin or should live elsewhere...