QmlProfiler: Deduplicate color selection and saturate colors some more

The original timeline colors are hard to see on certain devices. This
makes them stand out more from the background.

Change-Id: Icf6ef8a8ea360b7f47609f8673c4c6e22b091296
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>