Use vmagent instead of full victoria metrics

[lapo-luchini]

For those of us that already have an existing Victoria Metrics in the home network, but would prefer to use the local caching provided by vmagent (so that no data is ever lost, even if/when the external Victoria Metrics is unreachable), I created a fork of this project that does just that.

[fuslwusl]

This addon was meant to be a easy replacement for the influxdb addon. If you have some sort of special cases you can just fork an use your modified version.