Ability to use phone's light sensor to set watch brightness

The assumption is that phone and watch are used in the same environment, so should have similar brightness. Since a person most likely won't use their phone and watch at the same time, only update the watch brightness from phone's light sensor when the user turns off phone's screen. This also ensures that the phone is not in the user's pocket or other storage area where the brightness sensor values will not be accurate.

To be improved:
-Ability for users to set custom luminance to brightness values. (These values are currently from personal testing)
-Instead of using the light sensor and then setting the brightness based on that, maybe just directly use the phone's screen's auto adjusted brightness. From what I've seen, it's somewhat dubious whether you can get the auto-brightness adjusted value rather than just the baseline value. In addition, you need access to a view from the service, which while can be done, seemed too clunky for me.