#81 Add soap action response string to header file

[steph96]

The generated C++ code (-j) has the soap action string within the code for the request message for the proxy as well as for the service.
On the service side the response soap action must be entered manually for the soap_wsa_reply function call.
It would be much easier, if the response action is provided as a const char* or a #define in a generated header file (e.g., the service header file)