phidget driver

implemented new phidget driver

functionality:
-opens all attached phidget boards and publish analog and digital states from these boards
-the topicnames are "/analog_sensor" and "/digital_sensor"
-every attached board has three services: set_digital (sets an digital port), set_trigger_value(sets the change trigger value) and set_data_rate(sets the ports data rate)
-the boards services lies in a namespace named by the boards name or serial num
-the boards and their ports can be configured by params, see phidget_config.yaml for an example