Doc: update 3rd party license documentation

Task-number: QTBUG-33800
Change-Id: I7fc68a5d2ec25aa6f25f167075e33e1957301628
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>