fix minitaur.urdf: move lower-leg inertia to center, add missing collision for one of the motors, add contact parameters for friction_anchor, spinning friction, compliance (stiffness/damping)

fix in indexing for maximal coordinates (unused by default, still experimental, requires many iterations for Minitaur due to extreme mass-ratio, hence use of reduces/generalized coordinates)
modify quadruped.py to test maximal coordinates
wrap angular servo (positional) target within [-PI,PI] in btGeneric6DofSpring2Constraint
add 'j' key to show body frames in wireframe/debug mode

examples/ExampleBrowser/OpenGLExampleBrowser.cpp

@@ -221,6 +221,11 @@ void MyKeyboardCallback(int key, int state)
 			gDebugDrawFlags ^= btIDebugDraw::DBG_NoDeactivation;
 			gDisableDeactivation = ((gDebugDrawFlags & btIDebugDraw::DBG_NoDeactivation) != 0);
 		}
+		if (key == 'j' && state)
+		{
+			gDebugDrawFlags ^= btIDebugDraw::DBG_DrawFrames;
+		}
+
 		if (key == 'k' && state)
 		{
 			gDebugDrawFlags ^= btIDebugDraw::DBG_DrawConstraints;