fix($route): don't process route change controllers and templates for `redirectTo` routes

If a route defines a `redirectTo` value, the current route should stop processing the route
and instead wait to process the route of the redirect.

Currently, what is happening is that Angular detects a redirectTo value and updates $location,
but then continues processing the route that was intended to be redirected.
Templates are loaded, resolves are processed, ng-view then updates the view with a new template
and instantiates the controller all for a route that should have been redirected.

A common use case for assigning a function to the redirectTo is to validation authentication,
permission check, or some other logic to determine if the route should continue or redirect
else where. In the end, this happens, but in between, unexpected results may occur by updating
the view and instantiating controllers for logic that wasn't expected to be executed.

http://plnkr.co/edit/8QlA0ouuePH3p35Ntmjy?p=preview

This commit checks for a url change after a potential redirect, it the url changed, and is
not `null` nor `undefined`, exit out and don't process current route change.

Closes #3332
Closes #14658

BREAKING CHANGE

The $route service no longer instantiates controllers nor calls resolves or template functions
for routes that have a `redirectTo` unless the `redirectTo` is a function that returns
`undefined`.