Add the option of specifying a WB resampling matrix

Before this Merge Request (MR), the WB resampling matrix was systematically generated randomly by swe. The only control available on it was done through the optional specification of the random seed (--seed). Nevertheless, this is not enough if we want to be able to compare the results to those of the SPM toolbox. Thus, this MR has added an option to specify it through a vest file using --resamplingMatrix. Note that this option is currently hidden as I am not sure that we would like the users to use this option as they could supply a wrong resampling matrix. Note that if the corresponding vest file is not supplied, swe generate it randomly as before.