[touch-controller] Improve Head Slider and Lift Slider

[omarchehab98]

Problem

On touch devices, the sliders that control Cozmo's head and lift command imperatively. More specifically, dragging up orders the motor to rotate in a certain direction and dragging down orders the motor to rotate in the reverse direction. Since the angle of rotation is limited, it's hard for the user to precisely control the head and lift.

Potential Solution

Make the sliders declarative, meaning, the knob's position would reflect the position of the head/lift.