Optionally collect anonymous usage statistics

[declension]

As a mature project with no A-B testing or usage information, it's very hard to evaluate the success or even usage of browsers and plugins... or even numbers around QL users themselves (though see below)

Some carefully thought-out anonymous usage metrics would help here. They should be enabled / disabled by user preferences. Obviously there are considerations of formats, storage, protocols, etc, but it's doable and should help the longer term development of Quod Libet.

Debian Installation Stats

Whilst we're here, some encouraging Debian usage statistics.

[urielz]

+1 for this. I would happily participate.

[lazka]

Which reminded me of #1853