Replaced Chrome-specific mouse event property

With a standard equivalent. (Fixes a FireFox bug)
Fixed an IE-only problem

With event.dataTransfer
Local storage errors in IE no longer reported

They are only logged since they occur regularly.
Implemented scales

Only partially working with robots so far.
Updated comments and deleted commented out code

Using the convention that TODO: marks code I should return to.
Restructured top-level creation from JSON

The functions that reconstruction things from JSON are now distributed.
This means the set of widgets is no longer fixed by the table what was
in UTILITIES.
Fixed display problems with scales

Display of scales was repeatedly being updated.
Moved unused images to a new folder
Scales now fit into containers

E.g. box holes. Though the animating empty scales don't.
Scales now compute state on demand

And hence works even when not being displayed.
Added listeners to widgets

And scales listen for value changed events to update their appearance.
Improved generated descriptions of scales
Improved the CSS of robot conditions
Robot actions refer to scale sides

And not holes that they are implemented in terms of.
Moved a missing image file
Scales can compare element widgets
Simplified bird and nest backsides code
Scales now have custom backside

Though nothing special there -- but no longer share's box's backside
code.
Code sharing backside update code

Added generic code to backside.js
Introduced is_of_type for widgets

Cleaner than older code and a sub-class can override this.