[SecurityBundle] added short description and help for the init:acl command.

src/Symfony/Bundle/SecurityBundle/Command/InitAclCommand.php

@@ -31,7 +31,19 @@ class InitAclCommand extends ContainerAwareCommand
     {
         $this
             ->setName('init:acl')
-        ;
+            ->setDescription('Mounts ACL tables in the database')
+            ->setHelp(<<<EOT
+The <info>init:acl</info> command mounts ACL tables in the database.
+
+<info>php app/console ini:acl</info>
+
+The name of the DBAL connection must be configured in your <info>app/config/security.yml</info> configuration file in the <info>security.acl.connection</info> variable.
+
+<info>security:
+    acl:
+        connection: default</info>
+EOT
+            );
     }
 
     /**