Account for Material Emissivity in Longwave Temperature Map

[chriswmackey]

Right now, the thermal maps assume that the emissivity of the occupant is the same as all surfaces, making it difficult to study the impact of low-e materials directly on the MRT experienced by occupants.

I should at least account for this using an emissivity weighting factor as discussed here:

https://discourse.ladybug.tools/t/surface-emissivity-in-mean-radiant-temeperature-calculation-of-microclimate-map-analysis/13141/13?u=chris