QmlDesigner: Move creation method from QmlModelView to QmlItemNode

Change-Id: I087c4d6652d4f57e3c7682176e79253c0e378809
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
QmlDesigner: Move generateNewId to AbstractView

Change-Id: I8753eae6c4f79967822003709e7cd35dbea4eeba
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
QmlDesigner: Remove QmlModelView::createQmlItemNode functions

Change-Id: I5c3f05beec22f056daa3419fac40ef837a655a8d
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>