Implement getAcl method

[wallon-ines]

You forgot AbstractCmisObject modification in your pr. but with this modification It's work

diff --git a/src/DataObjects/AbstractCmisObject.php b/src/DataObjects/AbstractCmisObject.php
index 727807e..9477777 100644
--- a/src/DataObjects/AbstractCmisObject.php
+++ b/src/DataObjects/AbstractCmisObject.php
@@ -747,7 +747,8 @@ abstract class AbstractCmisObject implements CmisObjectInterface
      */
     public function getAcl()
     {
-        return $this->acl;
+        $result = $this->getSession()->getAcl($this, false);
+        return $result;

     }

     /**

In my Drupal, it's work too :