I'd like to move the display module up so that core and atom depend on it (rather than vice versa). This will have various nice effects such as - algebra and kernel tests that use display don't require building almost all of IMP - display can be used in core and atom C++ code to aid in debugging - code to display various decorators goes with the decorators - display now looks like statistics and algebra in that it provides low level services that can be used by many other modules

The externally visible breaking change caused by this will be that various display::Geometry subclasses for displaying decorators will be moved to other modules. Specifically: IMP::display::XYZRGeometry will move to core IMP::display::HierarchyGeometry will move to atom IMP::display::SelectionGeometry will move to atom

Objections, comments?