refactored backbone trace and simplified trace renderer base (e.g. removed trace subset class or overshooting concept)
careful examination of all spline related code, array access via .at instead of [] and other failsafe mechanisms placed to either avoid core dumps or locate them better, tweaked generated spline range to have proper spline-list size
added temporary interface for cartoon detail color range
fixed/improved refresh/rebuild behavior for entity and its renderer objects, especially for offscreen rendering purposes
re-added fast spheres for CPK rendering
removed a few unnecessary asserts and exceptions
removed some old undefed code



git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@2121 5a81b35b-ba03-0410-adc8-b2c5c5119f08