It's nice that you realized this needed to be abstracted more.  I've been planning for a while now to fold the breadcrumbs into the navigation framework with a new templatetag in hqwebapp/menu_tags.

*The names of the tabs, pages, and subpages that get displayed on one page are still defined in two separate places, one for the tabs and sidebar and one for the breadcrumbs.  Repeat: if we don't change this, the entire navigation hierarchy will need to be defined in two separate places.*  I think for the purpose of consistent language for users (i.e. "Project Reports" vs. "Reports") we should default to defining these strings only once, but even if not, we should define them *in the same place* with e.g. title_in_sidebar, title_in_breadcrumbs.

More on this in a bit.