Make Gallery example radio buttons exclusive.
Make Gallery example radio buttons exclusive.

Change-Id: I4bd9f53bf888f4fd1f9d85d6e572acc391822282
Reviewed-by: Morten Johan Sørvig <84fe11dd8bf63b99760f9a020e6b4a145681baec@nokia.com>

kobolabs/qtquickcontrols,richardmg/qtcomponents,richardmg/qtcomponents,kobolabs/qtquickcontrols,jfaust/qtquickcontrols,mizukusak/qtquickcontrols,jfaust/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols,jfaust/qtquickcontrols,richardmg/qtcomponents,mizukusak/qtquickcontrols,drgvond/qtquickcontrols