Nested guidelines for arrays and list

[brodieG]

Need a mechanism of tracking both the top level guidelines that belong to the actual high level structure (e.g. , , x, y, x for the array, $a$b$c for the list), but also want to have sub-guidelines in case the matrices or other objects contained therein are large enough to warrant having the guidelines.

For Arrays it's pretty straightforward, since we know the sub-object pattern. We just need a way of classifying "major" and "minor" guidelines. Lists are tougher since the sub-component could be anything, but there should be a reasonable way to parse the top level guides, and then dispatch on the sub-object to figure out how to find the minor guides.

[brodieG]

Logic here should help address stripping row headers from things in lists.

[brodieG]

Need to generate guidelines for each recursive object's top level, and then recurse depth first.

Arrays probably don't need much work here.

Guidelines will be identified by their text row number, and the depth of recursion they correspond to. We can then show the current guideline, and all guidelines of higher level (note, this is not necessary for lists, but is for S4 objects, some intricacies to deal with when we have alternating nested and S4 objects).