QmlProfiler: Provide a vertical scroll bar for the timeline view.
The timeline can be vertically navigated by flicking, which is not very appropriate for desktop applications. This change provides a scroll bar and mouse wheel scrolling in addition to that. Also it makes the vertical movement stop at the boundaries. The mouse wheel would exhibit unintuitive behavior without it. Change-Id: I5ef126525e452f46aa0a483a544345b8f618d829 Reviewed-by: Kai Koehne <firstname.lastname@example.org>