MAGETWO-52792: ACL node title stated as optional in xsd but required in logic

- fixed methods doc blocks

Author: Oleksii Korshenko

lib/internal/Magento/Framework/Acl/AclResource/Config/SchemaLocator.php

@@ -15,25 +15,26 @@ class SchemaLocator implements \Magento\Framework\Config\SchemaLocatorInterface
      */
     protected $urnResolver;
 
+    /**
+     * Initialize dependencies.
+     *
+     * @param \Magento\Framework\Config\Dom\UrnResolver $urnResolver
+     */
     public function __construct(\Magento\Framework\Config\Dom\UrnResolver $urnResolver)
     {
         $this->urnResolver = $urnResolver;
     }
 
     /**
-     * Get path to merged config schema
-     *
-     * @return string
+     * {@inheritdoc}
      */
     public function getSchema()
     {
         return $this->urnResolver->getRealPath('urn:magento:framework:Acl/etc/acl_merged.xsd');
     }
 
     /**
-     * Get path to pre file validation schema
-     *
-     * @return null
+     * {@inheritdoc}
      */
     public function getPerFileSchema()
     {