Use helm-chart for metrics server

[tuxpeople]

Switch to the helm-chart for metrics server. Its going to be released soon:

kubernetes-sigs/metrics-server#670

[onedr0p]

I have prepared for it

onedr0p/home-ops@d76b9d7

[tuxpeople]

@onedr0p that's a great idea. I'm also ready now :-) thanks!

I've put it into a separate branch: ada295b