Bug 29041: Improve specificity of breadcrumbs in Additional Contents

Bug 29041: Improve specificity of breadcrumbs in Additional Contents

This patch adds a link to news or HTML customizations in the breadcrumbs
navigation depending on which category of content you're adding or
editing.

To test, apply the patch and go to Tools -> News.

 - Begin the process of adding a news item.
 - In the breadcrumbs menu you should see:
   Additional contents > News > Add additional content
 - Clicking "News" should return you to the view of news items.
 - Test the same process in "HTML customizations."

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>