Config Option: Applies to administration pages

Problem/Motivation

Sometimes I just want to turn-off Easy Breadcrumb for administration pages.

It can be easier to manage on a site with a different Administration theme and admin pages that don't play well with Easy Breadcrumb.

Proposed resolution

Add a simple configuration checkbox, that is on by default, labeled "Applies to administration pages".

Take the code from the blog post here:

http://www.gregboggs.com/drupal8-breadcrumbs/

$request = \Drupal::request();
$route = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT);
// Do not adjust the breadcrumbs on admin paths.
if ($route && $route->getOption('_admin_route')) {

}

And use it in the method:

\Drupal\easy_breadcrumb\EasyBreadcrumbBuilder::applies()

Remaining tasks

Update the documentation
Write some tests

User interface changes

New configuration option to apply to administration pages - on by default or if never set before

API changes

None.

Data model changes

Update to config schema for new boolean config option.