restructure breadcrumbs

[chharvey]

Breadcrumb lists should have the following structure:

1. one nav for the breadcrumb list
   • An ol representing the descendant chain of the page
   • each li contains a link to the top, ancestor, parent, or this
   • for "this": keep href="#" but JavaScript onclick, show a ul containing siblings
2. another nav, not part of breadcrumb list, for other related pages, e.g. children or unrelated siblings

Markup all breadcrumb lists with Microdata ( #5 ).

Read https://github.com/chharvey/chharvey.github.io/wiki/Breadcrumbs for more info.