QmlDesigner: Add root item getter to ServerNodeInstance

Change-Id: I9f31390b478d8638038998682fb606dea5d1c81a
Reviewed-by: Marco Bubke <marco.bubke@digia.com>
QmlDesigner: Use only non threaded scene graph renderer

Change-Id: Ic74fbb319cc380442d3251af3ec0fbfc2bc3ad79
Reviewed-by: Marco Bubke <marco.bubke@digia.com>
QmlDesigner: Activate mockups in Qml

Change-Id: I1d8edd70cdec712f33c14adb241f7d805bba791d
Reviewed-by: Marco Bubke <marco.bubke@digia.com>