Add donor stats

Donor stats can be retrieved from the FAH API, the username configured in the client is used. This option can be enabled with -fah.api.

By default, the API is only queried every hour (it is pointless to ask for updates when no work has been submitted), this can be adjusted with the fah.api-throttle option.

Example dashboard has been updated with donor stats and the new metrics.

Breaking changes

• fah_reason removed, reason label added to fah_paused
• fah_eta, fah_queue_error, fah_state removed, labels added to new fah_queue_info gauge

Initial release

Builds for x86_64 based on the initial commit.