Add support for computing standard deviation in Aux_ComputeProfile

[HsunYeong]

Add Data_Sigma in Profile_t to store the standard deviation of Data, and compute it in Aux_ComputeProfile().

[hfhsieh]

I have left some comments.

@hyschive Should we enable this feature by default. I prefer to make it optional by adding a new parameter, such as const bool NeedDataStd, to Aux_ComputeProfile().

[HsunYeong]

Added parameter const bool GetSigma. It will skip some computation and set Prof[p]->Data_Sigma[b] to zero when GetSigma = false.