This is the interface for all writers. All writers, very simply, must
support a write method.
Writer and WriterFactory are part of the Writer framework. Folks who want
to use the emitter to generate stuff from WSDL should do 3 things:
1. Write implementations of the Writer interface, one each for PortType,
Binding, Service, and Type. These implementations generate the stuff
for each of these WSDL types.
2. Write an implementation of the WriterFactory interface that returns
instantiations of these Writer implementations as appropriate.
3. Implement a class with a main method (like Wsdl2java) that instantiates
an emitter and passes it the WriterFactory implementation