Summary:
Now you can pass a route to the pop function in the navigator context, and the Navigator will pop that scene off the stack and every scene that follows.
This changes the request API that bubbles up to the top-level navigator. The `pop` request had previously taken a route for `popToRoute`, but that is a more obscure use case. This makes the request API more closely match the context method naming.
@public
Test Plan: Verified this works by popping several routes in AdsManager. Experimented with UIExplorer Navigator example to make sure popToRoute still works as expected
Eric Vicenti