Inaccurate documentation

[monocongo]

The section in the README related to creating an unofficial service is not accurate.

The documentation shows that create_onvif_service should be called with a WSDL location, xaddr, and service name as arguments. The actual arguments for this function are the (service) name, from_template (unused), and portType.

Another aspect is that the create_onvif_service function can't be used as described to just create a service willy-nilly, but instead the service needs to be defined in the SERVICES dictionary declared within definition.py otherwise, an ONVIFError is raised within client.py.

Instead, it seems that what is necessary for a new service is to add an entry into the SERVICES dictionary declared within definition.py as well as a corresponding create_<name>_service function within the ONVIFCamera class within client.py.