[DI] Fix some docblocks

Author: nicolas-grekas

ContainerBuilder.php

@@ -710,8 +710,8 @@ public function getAlias($id)
      * This methods allows for simple registration of service definition
      * with a fluid interface.
      *
-     * @param string $id    The service identifier
-     * @param string $class The service class
+     * @param string $id         The service identifier
+     * @param string $class|null The service class
      *
      * @return Definition A Definition instance
      */

Definition.php

@@ -257,18 +257,38 @@ public function setArguments(array $arguments)
         return $this;
     }
 
+    /**
+     * Sets the properties to define when creating the service.
+     *
+     * @param array $properties
+     *
+     * @return $this
+     */
     public function setProperties(array $properties)
     {
         $this->properties = $properties;
 
         return $this;
     }
 
+    /**
+     * Gets the properties to define when creating the service.
+     *
+     * @return array
+     */
     public function getProperties()
     {
         return $this->properties;
     }
 
+    /**
+     * Sets a specific property.
+     *
+     * @param string $name
+     * @param mixed  $value
+     *
+     * @return $this
+     */
     public function setProperty($name, $value)
     {
         $this->properties[$name] = $value;
@@ -291,7 +311,7 @@ public function addArgument($argument)
     }
 
     /**
-     * Sets a specific argument.
+     * Replaces a specific argument.
      *
      * @param int   $index
      * @param mixed $argument