Add public filter/field in the API

Listing entries can now be filtered by “public”.
Creating or patching an entry can now set is to public or remove the public.
Entry response now include “is_public” boolean field

src/Wallabag/CoreBundle/Entity/Entry.php

@@ -687,6 +687,10 @@ class Entry
     /**
      * Used in the entries filter so it's more explicit for the end user than the uid.
      *
+     * @VirtualProperty
+     * @SerializedName("is_public")
+     * @Groups({"entries_for_user"})
+     *
      * @return bool
      */
     public function isPublic()