QmlProfiler: Pass model index to QML when selecting in trace view

This allows more precise specification of which event is supposed to be
selected.

Task-number: QTCREATORBUG-11945
Change-Id: Iff2e9bb8569711cc5df72a5ca55956e0091d6163
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Allow only one category per model in timeline

This simplifies the code a lot and allows for more flexibility
when interacting with the data.

Change-Id: I69630071eee66840e905fcd95ba8c708742d58b6
Reviewed-by: Kai Koehne <kai.koehne@digia.com>