Add BREAD_CRUMB_TRAIL.

This feature enables recursive printing of the bread crumbs for any
page, rather than just printing the parent group.
Merge branch 'feature-groupbreadcrumbs' of https://github.com/NimbusKit/doxygen into NimbusKit-feature-groupbreadcrumbs
Made bread crumb trails enabled unconditionally
Merge branch 'NimbusKit-feature-groupbreadcrumbs'