Add optimizing soil option

[1Dandan]

Name and Institution (Required)

Name: Dandan Zhang
Institution: Harvard University

Describe the update

Add the option to optimize soil sinks for normal errors.

[1Dandan]

Hi @laestrada, would you mind adding the update for the cases with state vector clustering?

[laestrada]

Yeah, I can do that at some point in a separate PR. The clustering case you are referring to is to prevent clustering of grid cells with positive total emissions and negative total emissions, correct?

[1Dandan]

Thanks @laestrada. Yeah, also the way we assign the perturbation scaling factor for the buffer state vector elements in regional GCC case. Then I will make this PR ready for review.