Updated some test files
Fixed bugs in img src error handling
Widget display not updated when not visible
Complete cleanup of rendering triggers

Much less unnecessary computation and simpler clearer code.
Fixed a CSS problem with robot conditions
Eliminated spurious warnings

When robot backside hidden
Improved number rendering

The font of the operator wasn't always being set so sometimes was too
small to see.
Fixed a bug hiding a running robot

Where sometimes when running unwatched would use the referenced widget
of the previous watched step.
Renamed variable for clarity
Added URL query parameter: reset

If the URL contains reset=1 then the saved state isn't not loaded.
Non-top nest widgets removed from container

So when they become the top they are displayed on the nest.
Non-top nest widgets hidden

Better than removing them from the previous container. And they may not
have a container yet if a drop of a fresh widget.
Birds now accept backsides

And they are scaled to fit on the nest.