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.
Reacting to IFileSystemInfo changes
Reacting to IFileSystemInfo changes
Fixing IFileSystem in Razor test
Moving IModelValidatorProvider to Options

Fixes #879
Removing unused namespaces
Fixing build break by updating comment
Prevent flushing when writing out from the formatters.
Also make the XML formatter respect object as a return type.

Issues: MVC/1073, MVC/972, MVC/958

1072 is a followup work item to add test coverage.
Updated to use the new target framework in project.json
Changed remaining ifdefs from K10 and ASPNETCORE50
Adding support for flush points in Razor pages

Fixes #1042
[Fixes #734] Attribute Routing: Implement Name

1. Added support for Name in attribute routing. Name can be defined using [RouteAttribute]
and the different Http*Attributes, for example [HttpGet].

2. Names defined on actions always override names defined on the controller.

3. Actions with a non empty template don't inherit the name from the controller. The name
   is only inherited from the controller when the action template is null or empty.

4. Multiple attribute routes with different templates and the same name are not allowed.
Updating FunctionalTests to use HttpClient abstractions
Take advantage of nameof to improve our usage of MemberData across the code base.

Substituted all instances of [MemberData("PropertyName")] for [MemberData(nameof(PropertyName))]
This change enables us to take advantage of IDE features like Navigate to source,
find all references, etc. When using Visual Studio.
Updated to use the new target framework in project.json