Generic broadening feature

[Rebecca-Nicholls]

Create a generic broadening feature that can create a spectrum given transition energies and intensities.

[Rebecca-Nicholls]

Need to write gendos.f90
Energy values will be read in a bands file format and intensities will be supplied in a formatted gendos.me file. The values will go into dos_calculate which will form a spectrum which will then be broadened by the broadening routines.