Fix an inadvertent 204 in activator tests

On a web server, this test ends up giving back a 204 because of the MVC
behavior when an action is declared to return void. The fix is to use
EmptyResult.
Adding a pattern for returning 'unhandled' exception information via
middleware.

This should be used where posssible instead of throwing an exception and
catching in a test, as that only works in memory.
Changed hard coded argument string in the throw to use nameof
Adding functional test for RazorViewEngineOptions.FileSystem
Adding additional functional tests for ModelBinding
Fixed folder name casing of Compiler/*
added few taghelper functional tests
removed the use of db
removed unused files