Added option to specify minimum bandwith for var bd nn KDE, as a potential workaround for 0 distance issue.
Added function to jitter points within grids to remove the majority(?) of duplicates.
Still seeing lots of duplicates afterwards, need to work out why so many.
Modified CAD-specific settings when applying PP - managed to get sensible convergence once, but may have since broken that.  TODO: investigate nan-matrix appearance after ~20 iterations.