hierarchy test fail should occur also at rmf writing and not at rmf reading only

[Pellarin]

the problem is that in Hierarchy.cpp we check whether a hierarchy is well built. For instance:

      if (!h.get_as_xyzr()) {
        TEST_FAIL("Leaf " << h << " does not have coordinates and radius");
      }

tests whether one of the leaves has coordinates and radius setup.

Now If I made a mistake, and one of the leaves does not have a radius (for instance an improperly built Gaussian particle), the rmfs from a complete calculation cannot be read again, unless I comment the lines above.

I think that either we check that during RMF writing we are saving a proper hierarchy and raise and error if we are not, or we simply warn the user during RMF reading if the hierarchy is not OK.