Add link to docs and modify docstrings to match PEP257

homeassistant/components/alarm_control_panel/demo.py

homeassistant/components/binary_sensor/demo.py

homeassistant/components/camera/demo.py

homeassistant/components/demo.py

homeassistant/components/garage_door/demo.py

homeassistant/components/light/demo.py

homeassistant/components/lock/demo.py

homeassistant/components/media_player/demo.py

homeassistant/components/notify/demo.py

homeassistant/components/rollershutter/demo.py

homeassistant/components/sensor/demo.py

homeassistant/components/switch/demo.py

homeassistant/components/thermostat/demo.py