Add application icon
Install GCompris

Install GCompris executable and its runtimes dependencies.
Also install Qt and Qml runtime plugins.
The CMake fixup_bundle function is called to:
 - create a standalone executable bundle on OSX
 - copy GCompris dll dependencies on Windows

Add qt_helper.cmake module to ease Qt and Qml plugins installation.
Workaround fixup_bunle taking ages on Windows

For some reason (cmake bug ?), fixup_bundle on Windows takes age when giving
additional libraries. So do not fixup Qt and Qml plugins. Fixing up GCompris
seems to be enough anyway.
Merge branch 'cmake-qsettings' of https://git-next.kde.org/kde/gcompris into cmake-qsettings
Merge branch 'cmake-qsettings' into masterGithub
Merge remote-tracking branch 'origin/masterGithub'