Clear the cache on `Strategy.Cluster` when features are removed.
Clear the cache on `Strategy.Cluster` when features are removed.

This prevents reappearing the removed features after zooming.

openlayers/ol2,owenmead/openlayers,ahocevar/ol2,wet-boew/openlayers,ahocevar/ol2,WayTo/openlayers,wet-boew/openlayers,boundlessgeo/openlayers,tschaub/openlayers-raster,shevawen/openlayers,openlayers/ol2,wet-boew/openlayers,boundlessgeo/openlayers,sanak/ol2,adh1365/openlayers,shevawen/openlayers,avinet/openlayers,altamiracorp/openlayers,v5analytics/openlayers,shevawen/openlayers,kartverket/openlayers,PublicStuff/openlayers,sbrunner/openlayers,kartverket/openlayers,PetrDlouhy/openlayers,pgiraud/openlayers,openlayers/ol2,adh1365/openlayers,ahocevar/ol2,sbrunner/openlayers,pgiraud/openlayers,pgiraud/openlayers,PetrDlouhy/openlayers,boundlessgeo/openlayers,pvalsecc/openlayers,sanak/ol2,sanak/ol2,dracic/openlayers,adh1365/openlayers,avinet/openlayers,pvalsecc/openlayers,elbakai/openlayers,georchestra/openlayers,Gnafu/openlayers,colllin/openlayers,elbakai/openlayers,elbakai/openlayers,PetrDlouhy/openlayers,owenmead/openlayers,v5analytics/openlayers,sanak/ol2,openlayers/ol2,tschaub/openlayers-raster,elbakai/openlayers,kartverket/openlayers,WayTo/openlayers,altamiracorp/openlayers,sbrunner/openlayers,altamiracorp/openlayers,colllin/openlayers,owenmead/openlayers,pvalsecc/openlayers,PublicStuff/openlayers,georchestra/openlayers,sbrunner/openlayers,pvalsecc/openlayers,owenmead/openlayers,pgiraud/openlayers,PetrDlouhy/openlayers,Gnafu/openlayers,WayTo/openlayers,Gnafu/openlayers,avinet/openlayers,wet-boew/openlayers,tschaub/openlayers-raster,PublicStuff/openlayers,Gnafu/openlayers,dracic/openlayers,v5analytics/openlayers,altamiracorp/openlayers,dracic/openlayers,colllin/openlayers,shevawen/openlayers,adh1365/openlayers,boundlessgeo/openlayers,georchestra/openlayers,PublicStuff/openlayers,kartverket/openlayers,WayTo/openlayers,avinet/openlayers,dracic/openlayers,v5analytics/openlayers,colllin/openlayers