Adding a logging sample utilizing NLog

As discussed a while back, I've added a logging sample utilizing NLog.

The purpose of the sample was :
- Demonstrate how logging can be done with NLog
- Demonstrate how to separate logs per class/per actor
- Demonstrate that Akka.Event.EventStream can be logged
- Provide a sample NLog configuration
- Me getting hands-on Akka.Net experience :)

How does the sample work :
Initially /user/supervisor is created. This is the actor that can create child Monitor actors and schedules monitoring checks on those children. Monitor actors are pinging websites and are checking if the sites are up. 

Each monitor actor contains a small "code-bomb" in the form of a D6 dice roll. Certain dice rolls will trigger NonFatalException/FatalExceptions to be thrown. Those are supposed to be handled by the supervisor. 

Each monitoring check result is sent to the /user/supervisor/processor actor which is logging the result.