added option for gfx cartoon twist hack

modules/gfx/pymod/export_render_options.cc

modules/gfx/src/impl/backbone_trace.cc

modules/gfx/src/impl/backbone_trace.hh

modules/gfx/src/impl/cartoon_renderer.cc

modules/gfx/src/impl/line_trace_renderer.cc

modules/gfx/src/impl/sline_renderer.cc

modules/gfx/src/impl/trace_renderer.cc

modules/gfx/src/impl/trace_renderer_base.cc

modules/gfx/src/impl/trace_renderer_base.hh

modules/gfx/src/render_options/cartoon_render_options.cc

modules/gfx/src/render_options/cartoon_render_options.hh