Add Support for EnergyWindowMaterialGlazingSpectral

[chriswmackey]

This should be relatively straightforward to implement. There should be a separate class for EnergyWindowMaterialGlazingSpectral that is distinct from EnergyWindowMaterialGlazing since the two materials have their properties defined in very different ways. I'm saying this because EnergyPlus IDF schema uses the same object for both cases and it makes things more confusing than they have to be.

The only challenge with implementing this is that the spectral material should still have properties like solar_transmittance so that it can play nicely with the methods on WindowConstruction as well as the methods that translate window constructions to Radiance modifiers.

For a first iteration, I think we can just compute a broadband solar_transmittance from the spectral data assuming a typical noon time solar spectrum.