UI feature: statistics / achievements / sharable

[Joachim]

The idea is to collect (or investigate whether the BOINC client is collecting this information already) run statistics (e.g. how many hours of computing) and have a easy to understand Statistics screen.

Based on this information, achievements could be issued like, "silver Android" for a certain number of hours.

Those achievements should be sharable on social media.

[Joachim]

David to add run time to core client. Use this in "contribution" tab. Make those contributions shareable. Make "credits" only show when advanced.

Allow users to invite people via social media at the and of the attachment screen and possibly later.