Adjust minPts without redoing aggregation

[guettel]

Our recommendation to choose the hyperparameter is to start with radius=1, reduce it until the number of clusters is only slightly larger than expected, and then increase minPts until the right number of clusters are obtained.

Could we add a function like

clx.minPtsChange(minPts)

which just redoes the minPts phase without doing the rest.

Note that, if mergeTinyGroups==False, then the group merging also needs to be redone because it depends on minPts. Otherwise, it doesn't.