Make a number of refactors to how the state of devices is set.

[kingsleyadam]

This is a refactor to how the state of devices is set. This should reduce the amount of duplicate code. Thanks @derjoerg for the suggestions on this one.

• Add new _state_refresh_output_pairings and _state_refresh_input_pairings to the Base class to store the pairings for refreshing the state of the device.
• Move self._refresh_state_from_outputs() to the Base class as we have to run this on each initialization of a device.
• Move the refresh_state function into the Base class and use the new _state_refresh_output_pairings to update the device state.
• For each device class move the _state and _brightness (if it exists) initial setter to the __init__ of the class itself. This should ensure the devices state properties always have a value, with an initial value of None.
• For the movment_detector class, it's possible it won't have brightness. Add a new test case where a movement detector doesn't have brightness but ensure the state of brightness is still set to a None value.