Better backward comptibility when enhancing configuration classes

[vchekan]

I've enhanced ProducerConfiguration class with new parameter, CompressionType. This keeps it source-compatible with previous version but binary incompatible. Method not found exception can be thrown if not all dependencies in a project using kafka4net are updated.

Rework config classes and move optional parameters into properties. This will allow to preserve both, source and binary backward compatibility.

Do this upon next major release because this is yet another API change.