Metric vis allows percentiles but doesn't support it

[lukasolson]

1. Create new metric vis
2. Select percentiles metric and apply

Nothing shows up in the visualization. I'm not exactly sure what should happen here. Should the percentiles selection not be available here? Or is there some way to actually show the percentiles in the vis?

[rashidkpc]

It feels like the metric vis should support multiple metrics and muti-value metrics. That said, I'm guessing it would be a good bit of work. I'd suggest removing percentiles from the metric vis, we can add support in 4.1.0