<vaadin-router> JS API (basic functionality)

[vlukashov]

As a developer I want to display different content on the page depending on the current URL. As a Polymer developer I want to do that with HTML markup, but I also want to interact with the router via a JS API.

DoD:

• the <vaadin-router> JS API allows
  -- adding / removing routes
  -- getting / setting the entire routes config
  -- getting / setting the router options
  -- triggering the router to re-render
• the <vaadin-router> JS API can be combined with its DOM API. e.g. the routes defined in the DOM are included into the list returned by the getRoutes() method
• add 2 demos
  -- basic <vaadin-router> JS API usage
  -- a combination of the JS API and DOM API

The common DoD applies.

[vlukashov]

Won't fix.