Add some error handling to the QWindowContainer example.
Add some error handling to the QWindowContainer example.

Use a QMainWindow and display errors occurring during loading
QML as well as scene graph errors (for example, failure
to create an Open GL context) in the status bar.

Change-Id: Id9cf190e8a4f40de0f18ab081e2747135221bb88
Reviewed-by: Laszlo Agocs <00c05606d635b5d8e1450a8536e4e2809abe4e80@digia.com>

mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d