fixed implementation of mFactor in ConservationEquation

it now works properly with moist air

This is for #131 
Could you please add an example. This example should then demonstrate that the current implementation is wrong, and if the fix is applied that the new implementation produces the correct results. 

I don't quite follow your reasoning as first you write "Consider the case where latent heat (both moisture and heat of evaporation) is added" and then you write "If the water were evaporated adiabatically". In the latter, you add liquid water and hence heat of evaporation is not added to the room. It is taken from the existing air in the room.

Let's do an example to convince that there is an issue, (and also address the inefficiency and wrong initialization).