WSDL elementFormDefault refinements

The qualified value for the elementFormDefault element in the XML schema should only be respected if the element on which is applied to not a global element.

For now, the first element is being checked, but in the future also other global elements (which are inmediate childs of the schema) should also have a prefix by default.

Next to that, the xmlns is only applied to elements without a prefixed namespace (prefix:).