Removing unused types

Fixes #1344
Fix unit test
Modify Razor components to use RazorViewEngineOptions.FileSystem
Fixes #1302
[Fixes #885] API Explorer: Link Generation

1) Expose the simplified relative path template by cleaning up constraints, optional and catch all tokens from the template.
2) Expose the parameters on the route template as API parameters.
3) Combine parameters from the route and the action descriptor when the parameter doesn't come from the body. #886 will refine this.
4) Expose optionality and constraints for path parameters. Open question: Should we explicitly expose IsCatchAll?
[Fixes #809] Multiple [Http*] verbs should create multiple actions
Adding RenderSectionAsync to RazorPage
Fixes #845
[Fixes #1331] Dispose HttpResponseMessage once its written out in HttpResponseMessageOutputFormatter
Ensure PDB writer component is available before emiting PDB
Ported from
https://github.com/aspnet/KRuntime/commit/36cd4901f6b13d135b82dd026768a37ee36bdedb

Fixes #1324
updating ILogger, see aspnet/Logging#3
Removing Microsoft.AspNet.Mvc dependency from ModelBinding
Add Html.Partial - sync versions of Html.PartialAsync

Fixes #1107
-Issue #913 - Model-binding is being case-sensitive when binding Url data to Enum parameter.
Fix: Using TypeConverter solves this problem.
-Issue #1123 - TypeConverterModelBinder cannot bind "byte" and "short".
Fix: Modified code to use TypeConverter which can handle these scenarios.
-Removing the GetConverterDelegate method and making the code similar to the WebApi.
Modify precompilation to always generate instrumentation
[Issue #1133] RedirectToActionResult and UrlHelper should use HostString, PathString, etc. To build Urls.

Added tests to describe the current behaviour with Unicode hosts.
React to options and hosting changes
Only load loadable assemblies
Adding HttpResponseException to WebApi Shim.
[Fixes #1216] Provide a property on JsonOutputFormatter to set serializer settings
[Fixes #1221] Rename OutputFormatter's WriteResponseContentHeaders to WriteResponseHeaders
[Fixes #932] Setting Json Serializer Settings
[Fixes #1283] Add functional tests for WebAPI-style controllers returning HttpContent
Addressed CR feedback