Port Serilog to support ASP.NET vNext

This PR includes - source code changes to port Serilog to support ASP.NET vNext (includes support for console, file, system.diagnostics to start with), smoke test updates. This also includes a temporary Demo project to show all the above features working on vNext. The Serilog.vs2015 solution is created SxS which includes the new projects as well so that people can still open the original solution without issues on VS 2013