AbsorptionChiller requires DHW load to function

[zolanaj]

But, CHP + SpaceHeating load should be viable. Likely issue is in this snippet of code:

https://github.com/NatLabRockies/REopt.jl/blob/029db01dc17ddfc726b3fc5bb7fb72b8541cff0e/src/core/reopt_inputs.jl#L204

Thanks to @Bill-Becker for pointing this out

[zolanaj]

#577 should fix this, new tests added to check moving forward