Improve nodejs webapp Quickstart:
Improve nodejs webapp Quickstart:

* Change document structure for consistency
* Add express-session middleware as dependency
* Add section on configuring express-session
* Add section on session management
* Section for routes (login, profile, logout)
* Helper function to check session
* Explain logout implementation is local only and add reference to logout docs for other options

jeffreylees/docs,yvonnewilson/docs,auth0/docs,jeffreylees/docs,yvonnewilson/docs,yvonnewilson/docs,auth0/docs,jeffreylees/docs,auth0/docs