add search argument and limit option to list users command

src/Wallabag/UserBundle/Repository/UserRepository.php

@@ -55,6 +55,19 @@ class UserRepository extends EntityRepository
             ->getSingleScalarResult();
     }
 
+    /**
+     * Count how many users are existing.
+     *
+     * @return int
+     */
+    public function getSumUsers()
+    {
+        return $this->createQueryBuilder('u')
+            ->select('count(u)')
+            ->getQuery()
+            ->getSingleScalarResult();
+    }
+
     /**
      * Retrieves users filtered with a search term.
      *