Change ThrowIfFaulted to WaitAndThrowIfFaulted
Issue #347: Throw a better exception when the user didn't add the MVC services.
Introducing MarkerService for identifying if MvcServices were added.
Remove `using` for Microsoft.AspNet.Mvc.Razor namespace from views
- eventually will clean up IntelliSense -- removing classes users don't
  need when editing a view
- will _not_ cleanup IntelliSense 'til VS stops using a private copy of
  Microsoft.AspNet.Mvc.Razor.Host.dll or we update that copy
- all tests and MVC sample views still work fine
- issue #969
Adding support for inheriting chunks from _ViewStarts as part of host
parsing.

Fixes #881
Update RazorView.RenderAsync to be virtual

Would be nice if this method is virtual so people can extend the RazorView easily, this functionality is available in the current MVC which I utilize.
Modifying RazorViewEngine to create IRazorView instances from service
container
Optimize attribute routing link generation
Adding ModelStateError if there is no input formatter selected.
Adding support for flush points in Razor pages

Fixes #1042
Moving FlushPoint behavior to RazorTextWriter