Revamped implementation to support FunctionTransform XalanNode input
* FunctionTransform now accepts xalan::XalanNode base xalan::XSLTInputSource instances as input parameter
** such xalan::XSLTInputSource instances were already supported for the stylesheet parameter but not for the input parameter
** e.g. it is now possible to generate a DOM inside a transformation, pass the DOM into a embedded transformation as input, modifiy the output of that transformation, pass this modified DOM into another transformation and so on... you get the point
* this required a revamp of TransformationFacade
** it is now a transformation independent wrapper for xalan::XalanTransformer
*** as such is was renamed to TransformerFacade
** removed error catching template factory method "try_create" as it is not needed anymore
** "std::basic_ostream<char>&" taking "generate" member method overloads were removed
** the set of "generate" member overloads was reduced to two methods accepting xalan::XSLTInputSource and xalan::FormatterListener as parameters
* the core problem first documented in 299d0f6 was solved by transforming the input parameter into a xerces DOM and wrapping this DOM inside a xalan::XercesDOMWrapperParsedSource instance
* serialization of the transformation result for file / std::cout output is now performed directly by the ixslt frontend
* removed 'stylesheet parameter' parameter from FunctionTransform
** the functionality provided by this is easily replicated using the now possible DOM input parameter
** this was done to simplify the interface and reduce unnecessary feature duplication
* updated FunctionTransform test case accordingly
* added "generate" template function to ixslt frontend
** wraps TransformerFacade and manages ist input arguments
** handles serialization to stream
* this commit marks a important milestone towards the goals defined in 741a70f