Limit the number of previews by running some clustering approach #125
Description
As we did in HiPiler, there should be an option to limit the number of previews we're showing.
This can either be done by simply not showing more than x previews or by employing some clustering approach and showing an aggregated preview.
Either way, we need to provide some indicator for how many items are on a pile or a general indicator showing that there are more items on a pile than shown by the previews. The option could be called indicatePileSize with the options visually and numerically.