Automatic embedding of a breadcrumb in pages

[brotkrueml]

As an integrator I want to embed the breadcrumb markup automatically. So far, I have to use the API or the breadcrumb view helper in a template to add the breadcrumb markup to pages.

Acceptance criteria:

• An extension configuration option was implemented: "Automatic embedding of the breadcrumb markup into the page
  ". The default option is not activated (for backward compatibility).
• If the configuration option is activated, the breadcrumb markup is added to a page.
• The breadcrumb list is generated from the rootline of a page.
• For the root page no breadcrumb list is embedded.
• The page property "Page enabled in menus" is respected (as it is also by a visible breadcrumb menu).
• The nav_title of the page is used for the name of the breadcrumb item when it is defined, otherwise title.
• The selected web page type from the page properties is used as value for the item @type.
• There is no check if another breadcrumb list is already added to the page, as multiple breadcrumb lists are valid and this could be intended.
• The documentation and change log are adjusted.