show containment relationships

[dhh1128]

When CESR attachment block begins, we see a code that says the type and the number of bytes that follow. Inside those bytes there may be a lot of interesting substructure. When the substructure ends, we'd like to show that the scope of the attachment block has also ended as well.

Possible ways to do this include:

• indenting substructure inside the container
• Creating nested containment boxes in the HTML output
• Writing some kind of an open and then a close delimiter (e.g., "{" and then "}") -- has the disadvantage that it might make people think those characters exist in the actual data
• Using partial transparency with background colors, so a container is red, the first content inside it is yellow but partly transparent, thus making it appear orange. All things inside a given box would thus be partly the color of the container.
• Writing a virtual "end tag" when the scope of a container ends.

Maybe a combination of these (indenting, partial transparency) would be best.

[dhh1128]

Suggestion from @SmithSamuelM: use annotated CESR