QmlDesigner: Add source property in ModelNode::isComponent

Change-Id: Ifb274c7589aa46350aa0fad788cc1abe4dbefbb1
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
QmlDesigner: Make model and view getter public

Change-Id: Iea753bda5239d68c6d51182e015344834cdf0f85
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>