Should be able to remove server from cluster

[pauldix]

If a node goes down permanently you should be able to remove the node from the cluster. Should remove it from cluster config and remove it from any shards.

[abelaska]

+1

[jvshahid]

This is done in a destructive way in #544, this story is different. This story aims at having a graceful way of removing a node from the cluster but move its data to a different node in the cluster.

[jvshahid]

Just to note that even destructively removing a node doesn't work all the time, there seems to be edge cases that causes the system to hang or sometimes the removed node returns to the cluster.

[beckettsean]

closing in preference for #1471 (such a good idea Paul keeps having it!)