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 <kai.koehne@digia.com>
QmlProfiler: Fix jaggy behavior of range start handle

The left handle of the range mover element didn't properly follow
the mouse movement. Also, a lot of code is duplicated between
RangeMover and SelectionRange. This change prepares RangeMover for
being reused in SelectionRange by eliminating external
dependencies.

Task-number: QTCREATORBUG-10762
Change-Id: Ia3b83101263e7af8ed46e1aaf4e92654b0068861
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
QmlProfiler: Use RangeMover to simplify and fix SelectionRange

Deduplicate the code and fix the "jaggy" behavior.

Task-number: QTCREATORBUG-10762
Change-Id: Iaca3bc5b77cb8d92f082232e6fd3c2d9e0935300
Reviewed-by: Kai Koehne <kai.koehne@digia.com>