Add trackPrefix to page object on events

[maxi-moto]

This is helpful when a view filters on a prefix and you want events specific to that view.

For instance, imagine setting environments on the same domain, differentiated by the prefix ('/internal/' and '/external/'), and you have views for internal and external filtered by the prefix. Now, events should be filtered to each view as well for accurate tracking.

[justinsa]

Thanks @maxi-moto. Change makes sense.

[maxi-moto]

Glad I can help!