QmlDesigner.PropertyEditor: Select first color if adding gradient

Change-Id: Idd4c7052e3dc4967fb2be243698c0ac023b1cbf9
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
QmlDesigner.PropertyEditor: Fix for LineEdit if editing a gradient

Change-Id: I7f83d7736b7dd0268420612ad1bd0f3b43c8617e
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>