Watched birds leave container and return

Earlier the view did so but not the bird itself. E.g. removed from box.
Box now displays properly while the bird is away.
Fixed a bug in shared widgets in JSON

If a shared widget was within another shared widget it sometimes was not
shared.
Improved robot dropping code

Moved code from unwatched to watched robot. Unwatched robots should run
as fast as they can and shouldn't need to check if they are watched.
Utility set_absolute_position fixed

It no longer clobbers input position.
Bird delivery improved

Birds deliver to a covered nest by setting down their message, moving
the nest contents, putting their message on the nest, and then restoring
the nest contents.
If vacuum clicked changes to next mode
Updated titles for vacuum clicking

Provides help that clicking switch to next mode.
Top-level workspace uses ToonTalk artwork

Looks like the 'floor'.
Numbers and boxes use ToonTalk artwork

Still needs some fine tuning. Fixes #128.
Fixed bug in determining if element animates
Removed obsolete code
Improving element highlighting code

Highlighting is no longer left behind on some drops into an empty hole.
Also all code now uses utilities functions rather than directly add and
remove CSS classes.
Nest no longer assumes only frontside contents

Changed to display backside as well if appropriate.
Improved CSS of numbers
Major rewrite of boxes

Elevated the status of holes so that it is hole objects that are always
inside of boxes and they have contents (or not if they are empty). Major
rewrite of how boxes are rendered.
Fixed highlighted problems

Highlighting went away prematurely.
Merge pull request #141 from ToonTalk/master

Updating gh-pages to master