Add a normal field formatter and a breadcrumb formatter

I just added the 8.x-1.x release, so we can mark issues with it.

A general note: We add a couple of configuration bits, so we should also add the corresponding config dependencies.

1. +++ b/src/Plugin/Field/FieldFormatter/MenuLinkBreadcrumbFormatter.php
   @@ -0,0 +1,161 @@
   +      $menu_links = [];
   +      $id = $items[$delta]->getMenuPluginId();
   +      $parent_ids = $this->menuLinkManager->getParentIds($id);
   +      if (!empty($parent_ids)) {
   +        foreach ($parent_ids as $parent_id) {
   +          if (!$this->getSetting('parents_only') || $parent_id != $id) {
   +            $menu_links[] = $this->menuLinkManager->createInstance($parent_id);
   +          }
   +        }
   +      }
   

   Could we use the MenuLinkTree here to save some lines of code?

2. +++ b/src/Plugin/Field/FieldFormatter/MenuLinkBreadcrumbFormatter.php
   @@ -0,0 +1,161 @@
   +      $links = array_map(function ($link) {
   +        if ($this->getSetting('link_to_target')) {
   +          $url = $link->getUrlObject();
   +        }
   +        else {
   +          // Set URL to none if we don't want to link to the menu link target.
   +          $url = new Url('<none>');
   +        }
   +        return Link::fromTextAndUrl($link->getTitle(), $url);
   +      }, $menu_links);
   

   Nice!

3. +++ b/src/Plugin/Field/FieldFormatter/MenuLinkBreadcrumbFormatter.php
   @@ -0,0 +1,161 @@
   +      // Set up the breadcrumb.
   +      $breadcrumb = new Breadcrumb();
   +      $breadcrumb->setLinks($links);
   +      $elements[$delta] = $breadcrumb->toRenderable();
   

   I love that these objects are reuseable.

Thank you for the contribution. Committed and pushed to 8.x-1.x