Lima/trap fix for geant4test

Fixes to a bug, in which trapezoid constructor based on 8-point list of corners were not properly building the side planes when called through the USolids interface (Thanks to Evgueni for this bug report).

In addition, improved the normal kernel, so points around edges and corners are averages of the normals of all surfaces around the edges or corners. This averaging was added with hopefully as minimal impact on performance as possible.