Currently the ownership of SelectableProxyModel instance
is assumed by QML engine, but we will use the following
rule to avoid that.

QML engine respects the normal QObject parent ownership
semantics of Qt C++ objects, and will never delete a
QObject instance which has a parent.

https: //doc.qt.io/qt-5/qtqml-cppintegration-data.html
Change-Id: Ifa37d14b8d74bfce050b0dee2949b42a7f784d3a