client/model/graph: add activityBus
client/model/graph: add activityBus

Very similar to Diff Bus, just includes initial clone commits. Will
remove it in the future.

ozFri/rhizi,Rhizi/rhizi,shlomif/rhizi,yuvadm/rhizi,tlevine/rhizi,yuvadm/rhizi,shlomif/rhizi,ozFri/rhizi,cben/rhizi,yuvadm/rhizi,ozFri/rhizi,cben/rhizi,shlomif/rhizi,Rhizi/rhizi,ozFri/rhizi,cben/rhizi,tlevine/rhizi,Rhizi/rhizi,cben/rhizi,tlevine/rhizi,yuvadm/rhizi,Rhizi/rhizi,shlomif/rhizi,tlevine/rhizi