removing cluster member (WIP)

Remove node from a cluster. See https://trello.com/c/xarZEs6g/846-ha-support-removing-nodes-from-clusters

https://github.com/crowbar/barclamp-crowbar/pull/1011 (or its roxy version) is needed so the remove role get correctly deleted after it is used once.
I dont think this is necessary.
And isn't this databag attribute used for the Crowbar UI order as well? 
If so it should definitely not be in here.