update devel/pyside2 and friends to 5.14.2

following r531601 (Qt 5.14.2), PySide2 can be updated, too

• pyside2-tools don't bring their own pyside2-rcc and pyside2-uic but use Qt's rcc and uic - patch cad/freecad to handle that
• remove Python 2 support: it's going to go away soon anyway, it did complicate these ports a lot, and it would have required more workarounds in FreeCAD when using Qt's rcc instead of the old pyside2-rcc.
• while here, do some polishing in freecad's makefile