opt-in "Popularity Contest"

Ratings are a frequently requested feature in F-Droid, but so far, we don't have the people or infrastructure in place to run a site based on user-generated content. We could instead do a lightweight version of this following the model of Debian's "Popularity Contest". We can have an setting called "Popularity Contest" then lets people opt-in, then F-Droid would report installs, install failures, and uninstalls to f-droid.org. We might be able to reuse the Debian server-side code for this. This can then also be used for "white label" clients to customize as well.

@larjona I see you've written about Debian Popularity Contest, any thoughts on doing this for F-Droid?