Use a custom cookiejar to avoid error when the cookie is badly saved

It happens sometimes on wallabag.it, the json inside the cookie is badly saved and the json isn't valid. It generates an exception and avoid people to use the api and import contents.
To fix that, we use a dedicated `FileCookieJar`, which extends the default one from Guzzle to fix these issues.

Also updated deps

src/Wallabag/CoreBundle/Resources/config/services.yml

@@ -82,7 +82,7 @@ services:
             - ["addSubscriber", ["@bd_guzzle_site_authenticator.authenticator_subscriber"]]
 
     wallabag_core.guzzle.cookie_jar:
-        class: GuzzleHttp\Cookie\FileCookieJar
+        class: Wallabag\CoreBundle\Helper\FileCookieJar
         arguments: ["%kernel.cache_dir%/cookiejar.json"]
 
     wallabag_core.content_proxy: