_StoreMixin: refactor collection cleanup out of _setCollection into _cleanupCollection
_StoreMixin: refactor collection cleanup out of _setCollection into _cleanupCollection

kfranqueiro/dgrid,kfranqueiro/dgrid,dylans/dgrid,dylans/dgrid,maier49/dgrid,maier49/dgrid,dylans/dgrid,kfranqueiro/dgrid,maier49/dgrid