Provide web-compatible stubs for {N} specific providers

[vakrilov]

There are a number of NativeScript specific services/providers/directives that can be injected in components. However, if you are sharing code with a web project all of those are not available.

It would be useful to provide stubs for those, in "web-compatibility" module to ease development of shared web/mobile components.

Providers to implement:

• RouterExtensions
• PageRoute
• ModalDialogParams

[NathanWalker]

• ModalDialogParams

[NathanWalker]

@vakrilov I have been planning a 3rd party lib to handle the web-compatibility layer here:
https://github.com/NathanWalker/nativescript-angular-web-tokens

If you are planning something similar inside this repo to be published with the renderer please let me know. I had originally thought it would be nice if for that to be provided as a 3rd party plugin since that is only needed for certain cases and avoid the added overhead here. Lemme know your thoughts.