Fixed #147: replica forests now supported with content-forests-per-host

I think I did that deliberately. It is for removing replica forests, and I am generating much more replica names as really need to be deleted, just to make sure nothing gets left behind for whatever reason. There is a check further down to make sure redundant names get skipped.

The other changes are indeed using setup:get-group, which plays together pretty nicely actually when you use multiple groups..