Servo library to detach servo after use


Trying to control servo from multiple patches in a state machine was not working with standard servo. This was my solution to fix the problem.

servo-enable: Standard servo node with Enable pin added. Detach servo when En is false and allow to free-wheel (or allow other node to control the servo).

servo-pulse: Merge servo and delay nodes to activate servo just long enough to move to new position based on previous position. Detach servo when timer is done.