Include overhang in BuildingShade model

[Mathadon]

The current building shade model only casts shade for a vertical object (e.g. opposite building) but in a very similar way there may be vertical object above the window that casts shade, e.g. from the story above which protrudes further outward or other type of overhang. I propose to integrate such shading object optionally in the same model.

[jelgerjansen]

@Mathadon this is indeed a nice feature, but isn't this already available via IDEAS.Buildings.Components.Shading.Overhang? If I understand correctly, the BuildingShade implementation assumes an infinitely wide construction that casts the shading, thus the Overhang model will always be more detailed, right?

Could you indicate the differences use cases for the "old" Overhang model and your new implementation? If we need both, it would also be good to indicate this in the model documentation.

[Mathadon]

@jelgerjansen that is correct. This implementation has the advantage of having two shadings in one. The DoubleShading could be used to combine two options too but it requires more code and the combination is also less accurate than the integrated model.