Visual Servoing based on fingertips

[hello-cpaxton]

From @hello-ck

• It looks like servoing attempts to center the object in the image rather than move the object with respect to the fingertips. This might cause issues with smaller objects that require greater precision. This is one of the benefits of performing servoing relative to the fingertips.
• Similarly, it looks like servoing attempts to move the median depth of the object to a fixed distance away from the camera. Since the depth of the fingertips varies with how far they've been closed, this could reduce performance with respect to smaller objects.