Introduce Mobile App as a Referrer Type

[#1]

In current state, the Referrer Type report does not provide a way to distinguish Mobile App traffic from Typed/Bookmarked traffic. It would be very helpful for the Referrer Type report to include "Mobile App" as a referrer type so that we can more accurately measure traffic coming to our site from our mobile apps.

Setting up a Marketing Channel for traffic from our mobile apps by configuring marketing channel processing rules that evaluate query string parameters included when our apps refer traffic to our website is one way of measuring this traffic, but it is only a partial solution which will help to allocate the traffic out of the Direct channel. To better understand the Referrer Type report, 'Mobile App' sources need to be distinguishable from Typed/Bookmarked within the Referrer Type report itself.