[commontk] Re-enable CMake support importing historical improvements from commontk/PythonQt fork

This commit partially reverts r431 (which removed unsupported files and added
documentation) and consolidates consolidates historical changes developed in
the `commontk/PythonQt` fork between 2011 and 2021.

Summary:

* Qt 5support:

  * Added initial and ongoing support for Qt5, including modules like `PrintSupport`, `QuickWidgets`, `Multimedia`, and `OpenGL`.
  * Removed Qt4 support; fixed CMake logic for building across Qt 5.3–5.9.
  * Introduced `pythonqt_wrap_cpp` macro and cleaned up legacy Qt macros.

* Build system enhancements:

  * Re-enabled and expanded CMake support with configurable install paths and testing.
  * Removed use of `INSTALL_NAME_DIR` to support relocatable installs.
  * Addressed build issues across toolchains (e.g., MSVC `/bigobj` workaround, debug mode fixes).
  * Added missing source files and build flags.

* Code quality and compatibility:

  * Replaced deprecated/legacy constructs (e.g., use of `nullptr`, fixed property aliasing with `name` → `objectName`).
  * Added support for 511 wrappers.
  * Resolved warnings and linkage issues with optional build flags (e.g., `PythonQt_Wrap_Qtcore`).

* Testing and cleanup:

  * Added cleanup/finalization unit tests.
  * Ensured test code compiles cleanly when wrapping is partially disabled.

Co-authored-by: Florian Link <[email protected]>
Co-authored-by: Matthew Woehlke <[email protected]>
Co-authored-by: Max Smolens <[email protected]>
Co-authored-by: Pat Marion <[email protected]>
Co-authored-by: Francois Budin <[email protected]>
Co-authored-by: Christoph Willing <[email protected]>
Co-authored-by: Stefan Dinkelacker <[email protected]>
Co-authored-by: Sylvain Bernhardt <[email protected]>

Author: 9 people