Improvements to charging

1) When charging, the PTU is turned so that the camera is facing the room. This allows to observe human activities during charging.
2) Collision prevention during the undocking process. The robot turns the PTU to check for obstacles when going backwards.
3) Head restart. The MCU 24V is switched off after successfull docking and turned on before undock. This causes the head to restart and reset its position that might be incorrectly estimated. MCU reset after undock causes the scitos_node to crash, therefore the scitos node must be respawnable.