Configure topology via a configmap

[ant31]

To be able to package correctly Heketi (e.g with helm/kpm, see #39) or have a smoother experience with kubernetes, it should limit as much as possible manual actions, like 'pushing the topology'

I would like to edit/create a configmap with the topology file to have it updated.

[sheerun]

Another idea is to capture topology in node labels. This eliminates the need to know node's hostnames and IPs before installing gluster-kubernetes.

The label could be something like:

• heketi.devices=/dev/vdb,/dev/vdc,/dev/vdd
• heketi.zone=1

[sheerun]

Also I'd suggest creating heketi-operator similar to etcd-operator:

https://github.com/coreos/etcd-operator