Fix rendering in Release mode

When using QVariant::value(), a variable needs to be created otherwise
performing QVariant::value<QMatrix4x4>().data() can result in undefined
behavior.

Change-Id: I546a5bc44e3a796f274f3e67e5a38d00e3a82fee
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
QRenderTarget: send QUuid for the attachments instead of clones

Change-Id: Ie86b3462f9eda3cfd70a997ef26422ed7cb2731d
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>