buildsystem - install the Python bindings into standard "site-packages"

Follow Python standards and install the bindings into
<prefix>/lib/pythonX.Y/site-packages

sync the Python cmake files with KDAB repository

python/examples/main.py

@@ -15,7 +15,7 @@ from MyMainWindow import MyMainWindow
 from PySide import QtWidgets, QtCore
 
 import sys
-import rc_assets
+#import rc_assets
 
 if __name__ == "__main__":
     QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)