(1) Add two functions to do the outlier elimination in the LSQ.
(2) Add new functions to estimate the formal uncertainties of VSH
parameters using the nonparametric bootstrap resampling technique.

Add the function for a standard outlier detection.

I added a new implementation to do the vsh fitting, however, it works slower than the first one. As a result, I will use the first one

First step of this longly delayed project. I implement the calculation of vector spherical harmonics.