Export feature adoption reports

The feature adoption reports contain very useful metrics, such as user and account adoption rate that give us a lot of insights into how well our product features are used. However, in order to visualize these metrics (see also: https://community.gainsight.com/px-product-ideas-23/spiderweb-charts-for-product-adoption-37278), I'd like to export them into a csv file for further processing.

cc @mickey and @angelo