Extension plugin

[rogerzanoni]

When running an example compiled with Qt 5.0, a runtime warning happens:
"Old plugin format found in lib /opt/qt5/qtbase/imports/QuasiGame/libquasigameplugins.so".

There's no documentation for QQmlExtensionPlugin used to export the plugin in qt5, but we have to fix this issue when they release some info about this class and the new way to export plugins.

[mdkcore0]

I'm working on it right now.