swagger: Document meaning of value -1 for parentId of TreeDataModel#191

bhufmann merged 1 commit intoeclipse-tracecompass-incubator:mastereclipse-tracecompass-incubator/org.eclipse.tracecompass.incubator:masterfrom

bhufmann:fix-tsp-bugsbhufmann/org.eclipse.tracecompass.incubator:fix-tsp-bugsCopy head branch name to clipboard