Virtual Routes Support (#1799)

* add first test

* new VirtualRoutes mixin that handles routes. fetch tries to use VirtualRoutes. default config updated

* cover all basic use cases

* regex matching in routes

* covered all virtual routes tests

* added hack to fix config test on firefox

* removed formatting regex matches into string routes

* added support for "next" function

* added docs

* navigate now supports both hash and history routerModes

* waiting for networkidle in navigateToRoute helper

* promiseless implementation

* remove firefox workaround from catchPluginErrors test, since we no longer use promises

* updated docs

* updated docs for "alias" as well

* minor rephrasing

* removed non-legacy code from exact-match; updated navigateToRoute helper to infer router mode from page

* moved endsWith from router utils to general utils; added startsWith util; refactored makeExactMatcher to use both

* updated docs per feedback

* moved navigateToRoute helper into the virtual-routes test file

* moved navigateToRoute to top of file

* updated docs per pr comments