A different option to expose fine tune customizations

@SimonCropp's PR #2304 is definitely a step forward in simplifying the nesting with lambdas but why not take it even one step further and get rid of the lambda all together.

So in this PR here is what I came up with for the Serializers:
```c#
Configure.With(b => {
    b.UseSerialization<Xml>()
      .DontWrapRawXml()
      .Namespace("Foo"));

});
```
So this way is also leaning on #2305.