.. the OverviewWindow class has been refactored to extract out the
core dashboard UX/UI into a new class ChartSpace.
.. additionally, a ChartSpace contains a set of ChartSpaceItem which
need to be subclassed by the developer.
.. for the Overview a set of OverwiewItem classes have been introduced
such as RPEOverviewItem, MetricOverviewItem and so on. These are
subclasses of the ChartSpaceItem.
.. The overview window implementation is now mostly configuration and
assembly of a dashboard using OverviewItems and the ChartSpace.
.. This refactor is to enable the ChartSpace to be used as a drop in
replacement for the existing TabView.
.. There are no functional enhancements in this commit, but the
overview chart shouls appear to be unchanged by the user.
