Improved CSS of conditions

By default they were too narrow.
Fixed robot suspension bug

Just introduced.
Fixed bug in closest_visible_ancestor

When it doesn't have an ancestor that is a side. Broke some animations.
Really fixed bug in closest_visible_ancestor

Previous fix was wrong.
Complete re-write of box display

Replaced HTML tables with absolute positioned elements. Seems that
mixing relative and absolute elements causes percentage CSS values to
skip generations. Also vertical boxes were broken and display correctly
now.
Better display of covered nests.
Added console warning and improved a comment
Fixed CSS of nests in boxes

Were being offset vertically
Widgets with an image fit in containers

Using background-size: contain when possible.
Added some error checking
CSS background-size improvements

Hatching eggs work better.
background-size now applied when loading

Widgets in box holes are now displayed at the correct size.
Bird animations were broken by background-size

The bird became very small and replicated as it flew.
Dimensions before fitting container saved

In the JSON and restored when loaded.
Replaced JQuery data with element attribute

JQuery's data primitive wasn't behaving reliably and using element
attribute is simpler. Hopefully this won't interfere with garbage
collection.
Enabled training of a robot as next robot

It finds the context if the robot is trained in the other robot's drop
area for the next the robot to run.
Close buttons are now always on top of widgets

Fixes problem where clicking on the close button opened the backside
instead.
Fixed typo in recent revision
Commented out obsolete code
Commented out obsolete min-width

And min-height CSS. I think they are obsolete now.