FIX: backbone repr coloring may fail
FIX: backbone repr fails for 1 residue fibers
FIX: hyperball drawn as licorice (when impostors are disabled) not updatable
FIX: picking may fail
CODE: minor enhancements
FIX: BufferVectorHelper
FIX: shading seems in CylinderGeometryBuffer from wrong normals
WIP: render unlit background group