Router: Missing Generate URL's documentation

The main router documentation is missing some commonly used functions:
`generate`, `navigateTo`, `route-href` and a bit off-topic but `NavigationOptions` used in `navigateTo`

Cheat sheet has a section for `Generating Route URLs` that would be a good base for the new documentation.

It has been a pain for far too long. Time to add it to the docs guys!

Start with the main router documentation and the cheat sheet's “Generating Route URLs” section. Document the commonly used generate, navigateTo, and route-href functions, plus NavigationOptions as used by navigateTo. Done means the main router documentation covers these items with the cheat sheet as a consistent reference.

Written by the indexing model from the issue text.