HouseFly 2.20.0 — someone else's decision stands

2.19.0 let a fly see a lamp as it is, and the first thing that showed on the
demo box was a fly switching a light back on two to fourteen seconds after the
house's own automation had switched it off — four times an hour on one light.
A person turning off a lamp a fly may touch would have met the same.

A fly now leaves alone anything someone else changed recently: for an hour
after a person (a logged-in user, or a device reporting its own change, which
is what a wall switch looks like), and for ten minutes after an automation, a
script or another fly. It knows which is which from the context Home Assistant
stamps on every change; every fly registers its own, so it can tell another
fly from a person, and a restart's restored states count as nobody's.

Counted as total_left_to_others, apart from total_already_as_wanted and
from total_blocked. Five new checks in section 10c of tools/validate.py.