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.