Add logging and tracing

[yallie]

Remote calls and events are hard to debug.
JsonServices server needs basic support for logging internals:

1. authentication
2. remote method calls
3. subscriptions
4. unsubscriptions
5. event invocations
6. user sessions

There should be support for positional arguments like Console.WriteLine

Log("This is a message to {0}: {1}", userName, message);

and named arguments for structured logging frameworks like Serilog:

Log("This is a message to {userName}: {message}", userName, message)