Added default_cluster_groups property in Kwik model.
Added default_cluster_groups property in Kwik model.

rossant/phy,nippoo/phy,kwikteam/phy,kwikteam/phy,kwikteam/phy,rossant/phy,nsteinme/phy,nippoo/phy,rossant/phy,nsteinme/phy