* Add person component
* Required first name.
* Optional last name and user id.
* Optionally track device trackers. Last device tracker state change will
set state.
* Set device tracker state entity_id as source attribute.
* Set coordinates of device tracker state as state attributes.
* Restore state.
* Parse restored state too
* Clean up
* Add missing property decorator
* Validate source entities as device trackers
* Only use name instead of first and last name
* Add user_id validation
* Add unique_id
* Remove not needed properties
* Uniform docstrings
* Fail component setup if no valid entities
* Add tests
* Add id and use that for unique_id
* Clean up
Martin Hjelmare