lib: Add helper to remove tracking from URIs

This function, based on the PureURL Firefox add-on, will strip
tracking information from URLs, such as analytics information.

See https://addons.mozilla.org/fr/firefox/addon/pure-url/

https://bugzilla.gnome.org/show_bug.cgi?id=720520
Remove analytics from browsed URLs

When using "Do not track", also remove analytics information
from URLs using the new URI helper.

https://bugzilla.gnome.org/show_bug.cgi?id=720520