Better documentation for subclassing QQuickItem
Better documentation for subclassing QQuickItem

Task-number: QTBUG-26025

Change-Id: Ia0fadf54ee8924f9892bc567c107efc4dca80628
Reviewed-by: Martin Jones <d1da02505c7f228af82a23235becb435f45569f5@nokia.com>

mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,jfaust/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,corngood/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,jfaust/qtdeclarative