Adding ElmahExceptionLogger implemented ExceptionLogger

- Updating nuget packages to latest
- Updating nuget.exe to ver. 2.8.0
- Adding `ElmahExceptionLogger` implemented `System.Web.Http.ExceptionHandling.ExceptionLogger` as it is at [ASP.NET](https://aspnet.codeplex.com/SourceControl/latest#Samples/WebApi/Elmah/Elmah.Server/ExceptionHandling/ElmahExceptionLogger.cs)