QmlJS: Move ensuredGetDocumentForPath to  ModelManagerInterface

The new function does properly update the latest snapshot.

Change-Id: If3148701e2f98c39a0822d1395b43f4fa7ee1949
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
QmlDesigner: Add puppet stop message box

You must set DEBUG_QML_PUPPET as environment variable.

Change-Id: I072ac22d2f835781e93401e4a3b876fce6e4b2e0
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>