New: added self hosted analytics to help improve nzbdrone.

@markus101 @Taloth 

This will send very general information about browser/os and which urls the users visit. I even anonymized the url so if you are accessing nzbdrone using your own private domain it won't be sent to us. everything is reported as `http://local/`

It can be turned off in Config>General and not even under advanced settings.

All the info will be sent to servers hosted by ourself (Piwik) so no third party will have access to the info (even though there is really nothing there).