Bug 447259 - modified handling of row selection with modifier keys to
have a consistent handling
Bug 447261 - lastSelectedRegion is set to null in case of row selections
using the CTRL modifier
Bug 379890 - updated the _5123_SummaryRowPositionExample to also use the FixedSummaryRowLayer in order to correctly handle scrolling
Bug 453219 - PopupMenuBuilder now adds a DisposeListener for disposing the created Menu to NatTable