KDSoap 2.0.0

In release 2.0.0

General:

• Supports Qt6 in addition to Qt5
• Minimum Qt version is 5.9
• The qmake buildsystem (via autogen.py) is removed.
• buildsystem: a new 'docs' target is created when CMake -DKDSoap_DOCS=True.
• buildsystem: the API manual is now generated in build/docs vice source/docs.
• buildsystem: added an uninstall target
• buildsystem: generate and install kdsoap-version.h
• The API manual is generated+installed in qch format for Qt assistant.

Client-side:

• Added options to the KDSoapClient specifying the SOAP action sending method

WSDL parser / code generator changes, applying to both client and server side:

• Fix generated code in case a variable is called "d" or "q" (#118)
• Fix generated code for an enumeration type with a length restriction (#234)
• Avoid potential type collisions in nested complexTypes (#239)