SAM snow losses overestimate losses for bifacial systems

[brtietz]

Snow losses are applied to DC energy, which means that if the snow model computes a 100% loss, 100% of the energy is lost. However, this is only true for the front side of the system, so ignores contributions from the back side of bifacial panels when the front side is covered.

See if there's a quick fix to improve this or if it needs to be a larger project (close if the latter).