Clusters dashboard

Totally work in progress, but at least applies now (after lying dormant for 3 months). Not sure if it even works, to be confirmed... I also need to do a massive rebase to make sure it looks like I know what I'm doing. Use at your own risk.


Note that there's a FIXME for this commit: https://github.com/bkutil/barclamp-crowbar/commit/a0790b6c3d587d4f49aa3060d2d9fbcf592c65b9

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