Automatic cluster (and popup) update after underlying markers modifications

[julien-deramond]

Automatic cluster (and popup) update after underlying markers modifications (force the recalculation of the clusters).

Eventually verify if there is a configurable periodic refresh in automatic clusters in Leaflet?

In fact, redrawAll() does this refresh --> could we consider that's OK (up to the developer) or could be add it "only when it's useful"?