Code cleanup
minor: variable renaming
Added empty view to SliceViewer (switching RBV (DEM) and SliceViewer is still buggy)
Fix for error when changing split views
Merge branch 'empty-volume-view' into fha-next
SliceView: Cleanup event bindings
Added 'BaseView' for context binding, resize and empty view management. Ported 'SliceView' to use the BaseView.
Some changes in 'BaseView' and ported over RectangularBoxView
fixes for last commit