tweak ImportMJCFSetup.cpp example MJCF humanoid a bit, clamp target positions to be within joint limits to avoid solver problems (conflicting constraints)

add humanoid_manual_control.py PyBullet example which is similar to ImportMJCFSetup.cpp

src/BulletDynamics/Featherstone/btMultiBodyConstraint.h

@@ -119,6 +119,14 @@ public:
 		return m_bodyB;
 	}
 
+	int getLinkA() const
+	{
+		return m_linkA;
+	}
+	int getLinkB() const
+	{
+		return m_linkB;
+	}
 	void	internalSetAppliedImpulse(int dof, btScalar appliedImpulse)
 	{
 		btAssert(dof>=0);