Enable HttpRequest APIs dependent on VirtualPathUtility

[twsouthwick]

Summary

A number of APIs on HttpRequest rely on the VirtualPathUtility. Once that's available (#83), these APIs may be built on it.

In scope

• HttpRequest.FilePath
• HttpRequest.PathInfo
• HttpRequest.PhysicalPath
• HttpAppPathModifier

[CZEMacLeod]

HttpResponse.ApplyAppPathModifier is used for cookieless session handling - so I don't think is in scope.

FilePath and PathInfo, other that the trivial implementation which would match MVC5 and WebApi2, don't quite seem to have an equivalent in AspNetCore. They only come into effect when a filetype in mapped to a handler in IIS, and that effectively becomes the 'script' that is running, and anything after the path to the file, is treated as PathInfo. This seems mainly to fit webpages use where the 'script' is the .aspx file.
I'm not sure there is an easy way this fits in AspNetCore terms, as everything is just done with endpoint routing.

I have done the basics for

• HttpRequest.PhysicalApplicationPath
• HttpRequest.PhysicalPath
• HttpRequest.PathInfo
• HttpRequest.FilePath

If you want it - CZEMacLeod@16a9820

[CZEMacLeod]

@twsouthwick If you add IHttpHandler to the mix, it makes sense to map FilePath and PathInfo as they relate to the handler.
I did a quick version of IHttpHandler here https://github.com/CZEMacLeod/systemweb-adapters/tree/czemacleod/ihttphandler

This includes

• IHttpHandler
• IHttpAsyncHandler
• IHttpHandlerFactory
• HttpContext.CurrentHandler
• HttpRequest.PathInfo
• HttpRequest.FilePath
• HttpRequest.PhysicalApplicationPath
• HttpRequest.PhysicalPath

Also for Core:

• HttpHandlerBase
• HttpHandlerMiddleware
• HttpHandlerFactoryMiddleware
• RewriteScriptResourceType
• HttpHandlerMiddlewareExtensions
  • IApplicationBuilder.UseHttpHandler - An extension method allowing you to add IHttpHandler and IHttpAsyncHandler to a aspnetcore application (with parameters closely matching the tag from web.config.
  • IApplicationBuilder.UseHttpHandlerFactory
  • IApplicationBuilder.UseHttpHandlerMiddleWare
  • IApplicationBuilder.UseHttpHandlerFactoryMiddleWare

Also fixes for HttpRequest.AppRelativeCurrentExecutionFilePath and HttpServer.MapPath due to the difference between Path and FilePath when PathInfo is not empty.