[UX] Breadcrumb should include Primary/Secondary tabs

From @klonos in #2246

1. Please don't get me wrong. The breadcrumb looks OK when there are multiple crumbs, but here's how it currently looks when there is only one crumb and no secondary tabs (that's my 1.5.0 local with the primary tabs visible since I'm logged in):

(notice how the eye needs to move up and down to follow the trail)

...and here's how it looks in the PR sandbox (not logged in, so no primary tabs):

The PR is better (less visual emphasis), but still not that great IMO. It's just a horizontal bar across the screen that draws unnecessary attention. Which brings me to... 1. In my head, I want the combination of breadcrumb > page title > primary tabs > secondary tabs to be a visual trail of where I am at. The way we have it now, it is page title > primary tabs > secondary tabs > breadcrumb. I don't think that this works that well. The breadcrumb should not come between the title/tabs section and content if you ask me.

...we are doing it so much better in the admin layout:

You can see that clearly if you switch using Basis as the admin theme:

I'm not saying that the breadcrumb belongs in the header, but it needs to be coming before the page title. Unfortunately, the page title pseudo-region (actually a pseudo-block) cannot be moved around (#933).

From @olafgrabienski in #2246:

In my opinion, the situation when there is only one crumb, is even misleading. Unless you have a more nested page structure on a website, the breadcrumb looks like there is just another "Home" link on the page. Adding the current page as an unlinked crumb would improve the situation a lot.

This (as the position of the breadcrumb) seems to be theme agnostic though. Structurally, you get the same result in Bartik at least.