PyBullet: add signed distance field support, with example/signedDistanceField.py

See also data\toys\concave_box.urdf and data\toys\concave_box.cdf

data\toys\concave_box.cdf was generated from concave_box.obj using
//GenerateSDF.exe -r "32 32 32" -d "-1.6 -1.6 -.6 1.6 1.6 .6" concave_box.obj
//SDF is based on code from DiscreGrid, https://github.com/InteractiveComputerGraphics/Discregrid

examples/ExampleBrowser/OpenGLExampleBrowser.cpp

@@ -410,6 +410,14 @@ void OpenGLExampleBrowserVisualizerFlagCallback(int flag, bool enable)
     if (flag == COV_ENABLE_WIREFRAME)
     {
         visualWireframe = enable;
+		if (visualWireframe)
+		{
+			gDebugDrawFlags |= btIDebugDraw::DBG_DrawWireframe;
+		}
+		else
+		{
+			gDebugDrawFlags &= ~btIDebugDraw::DBG_DrawWireframe;
+		}
     }
 }