limit_vars is not optimal #44
Description
The limit_vars option works fine, but it is not optimal, because it still does all calculations for all variables, which takes a bit of processing power. I couldn't see an obvious way around this, because some variables rely on each other during the computation (e.g. RH/VPD).
This is not urgent, but it would be nice if some of these computations could be skipped, to speed up conversion when not all variables are needed.