Refactored base test classses.

Split generator specific code into a  code generation class which is broadly usable and a functional test class usable for reading WSDLs and testing generated files.
Finished implementation date time handling.

- Convert SOAP datetime to the PHP DateTime class
- Removed option for enabling this. This should be the default behavior.
- Implemented unit and functional test.
Implemented initial support for method type hinting

- Only supports DateTimes (and arrays) for now
- Updated test cases accordingly