Disable hyperlink auditing beacon

Background information

See "Hyperlink-Auditing aka <a ping> and Beacon aka navigator.sendBeacon()".

Chromium-based browsers

For those browsers, the network requests fired as a result of calling navigator.sendBeacon() are sent as behind-the-scene network requests.

Caveats for browsers based on Chromium version 48 or less

Network requests created as a result of web pages using navigator.sendBeacon() will not be blocked when the setting "Disable hyperlink auditing/beacon" is checked. This is a limitation of the chrome API prior to v49, as network requests fired as a result of calling navigator.sendBeacon() are reported as the generic type other by the browser.

The webRequest API was extended in Chromium 49 to support new request types, and thus the setting works fine for any browser based on Chromium 49 or higher, as there is now a specific network request type, ping, which uBO normalizes to beacon -- and hence can now filter correctly.