Add Wavefront as a remote write

[puckpuck]

@brian-brazil can you please take a look? This adapter is already deployed at multiple locations in production today.

[brian-brazil]

Can you add the DCO?

Looking at your code, note that there's no requirement that timeseries from Prometheus have an instance label which would result in an empty source - which I believe Wavefront will reject. Also, underscore is a valid character in Wavefront metrics names, so there's no need to sanitize it.

[puckpuck]

DCO done.

Empty source does not get rejected by Wavefront, it will get set to "unknown" if missing.
Wavefront's UI creates hierarchies from metrics based on the .. Converting a _ to a . of the metric name to take advantage of the UI benefits is this is the typical use case for Wavefront.

[brian-brazil]

Thanks!