whenever the window got activated.
New DataView::MakeVisible() makes sure the specified position is visible
in the view, and scrolls to it if not (both, horizontally and vertically).
Implemented cursor navigation and selection extension in the DataView class.
Fixed a bug in DataView::SetSelection() that could let slip through invalid
values.
Renamed DataEditor observer notices.
git-svn-id: file:///srv/svn/repos/haiku/trunk/current@6634 a95241bf-73f2-0310-859d-f6bbb57e9c96