Remove ancillary serilog dependencies

[chrisdrobison]

Is there any reason for this SDK to take a dependency on anything but the core Serilog library? All the logging configuration should be handled by users of this library, not the library itself. The latest core serilog library supports all the .NET and .NET Framework versions you guys need, the problem is the reference to all the other serilog libraries such as the sinks, which IMHO, this library should not be referencing or configuring at all.