Bug 32507: Use template wrapper to build breadcrumb navigation

Bug 32507: Use template wrapper to build breadcrumb navigation

This patch lays the groundwork for updating the way we build breadcrumb
navigation on each page, and implements it on the cities administration
page as a proof of concept.

The page creates two blocks, 'breadcrumbs' and 'breadcrumb_item'

'breadcrumbs' builds the outer structure of the menu, currently:

    <nav id="breadcrumbs" aria-label="Breadcrumb" class="breadcrumb">
        <ol class="breadcrumb">

It automatically adds the "Home" link which appears on all pages.

The 'breadcrumb_item' block builds the list item which contains the
individual link.

To test, apply the patch and go to Administration -> Cities & towns. On
each variation of the page, check the breadcrumbs menu:

 - On the initial summary view it should be:
   Home -> Administration -> Cities
 - Click "New city" and the menu should be:
   Home -> Administration -> Cities -> New city
 - When you edit a city:
   Home -> Administration -> Cities -> Modify city
 - When you delete a city:
   Home -> Administration -> Cities -> Confirm deletion of city

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 8a01c095b7ec3ef6947148ad3b7771fd01603bc8)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>