- A new score IMP::core::BoundingBox3DSingletonScore has been added to keep particles in a box.

- str should now work better in python when applied to IMP::Object objects and a few others. Objects should use the new IMP_SHOWABLE and IMP_SHOWABLE_INLINE macros instead of declaring show functions directory to make it so that they work in python. It is now a bug for print or str to not return something useful in python for any IMP object.