Include sync errors in ListControllers result

[squaremo]

We now keep track of individual sync errors (failure to kubectl apply a resource). We could include this information in the output of ListControllers, so it can be shown by fluxctl list-controllers (for example).

[rndstr]

We now keep track of individual sync errors

where?

[squaremo]

We now keep track of individual sync errors

where?

"keep track" is possibly a little generous. I mean that we try to apply everything, and if that fails, we apply things individually -- so we see individual failures, if there are any. In https://github.com/weaveworks/flux/blob/master/cluster/kubernetes/sync.go#L116 and ff.