[IMP-dev] [Bug 114] Use directions from higher up in the tree when doing EV on rigid bodies

https://salilab.org/imp/bugs/show_bug.cgi?id=114

--- Comment #1 from Daniel drussel@SALILAB.ORG 2010-08-06 21:30:21 PDT --- Even better might be to use the hierarchy on the particles. That is pretty tricky as we would have to also take the traits (instead of the refiner, perhaps). Could just be an alternate constructor that for now just makes a leaves hierarchy. But really, why bother.

Instead, lets make a rigid body ev pair score and use that. It will find all the pairs, walk up the tree to merge some and then add directly to the rigid body derivatives.