Track chart datapoints from their sources and provide a tabular view of chart data

Summary: Depends on D20815. Ref T13279. Give datapoints "refs", which allow us to figure out where particular datapoints came from even after the point is transformed by functions. For now, show the raw points in a table below the chart.

Test Plan: Viewed chart data, saw reasonable-looking numbers.

Subscribers: yelirekim

Maniphest Tasks: T13279

Differential Revision: https://secure.phabricator.com/D20816