Ability to enable/disable downloading images

This will speed up the test suite because it won’t download everything when we add new entry…
Add a custom test with downloading image enabled

src/Wallabag/CoreBundle/Command/InstallCommand.php

@@ -398,6 +398,21 @@ class InstallCommand extends ContainerAwareCommand
                 'value' => 'wallabag',
                 'section' => 'misc',
             ],
+            [
+                'name' => 'download_images_enabled',
+                'value' => '0',
+                'section' => 'image',
+            ],
+            [
+                'name' => 'download_images_with_rabbitmq',
+                'value' => '0',
+                'section' => 'image',
+            ],
+            [
+                'name' => 'download_images_with_redis',
+                'value' => '0',
+                'section' => 'image',
+            ],
         ];
 
         foreach ($settings as $setting) {