QmlDesigner: Remove unstable feature

Change-Id: I30ac5110a504ae71e6b084fc32a50bd875bf136b
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
QmlDesigner: Remove untested code

Change-Id: Ia6343b28fc7a42f9380e7151d28eb781428e894d
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>