fixes some frame logic issues caught by trying:
```
terrain = RigidBodyManipulator(['sdf/drc_practice_task_',num2str(task_number),'.world']);
x0 = Point(getStateFrame(terrain)); % all zeros
v = terrain.constructVisualizer();
v.draw(0,x0);
simulate(cascade(terrain,v),[0 5],x0);
```
ignore self collisions
Merge pull request #654 from RussTedrake/frame_fixes

Frame fixes