Update changelog

Author: ywarnier

documentation/changelog.html

@@ -200,6 +200,7 @@ <h4>For developers and sysadmins</h4>
         </ul>
         <h3>Improvements (minor features) and debug</h3>
         <ul aria-role="log" aria-live="off">
+            <li>[2018-08-15] (<a href="https://github.com/chamilo/chamilo-lms/commit/47c76fdb8f45c33bf8bc8c6e2543476fe7492274">47c76fdb</a>) Add missing statistics_na.png icon</li>
             <li>[2018-08-14] (<a href="https://github.com/chamilo/chamilo-lms/commit/cd6e9dcac60d2197ee6a02d779b9edbf664a493a">cd6e9dca</a>) Portfolio: Fix portfolios list in social network (void the course context to avoid showing only portfolios from one course)</li>
             <li>[2018-08-14] (<a href="https://github.com/chamilo/chamilo-lms/commit/fd944a29fb95cd4cadf34f3eb11f9f6b5a6b6ac8">fd944a29</a>) Portfolio: Add instructions about course portfolio activation to main/install/configuration.dist.php</li>
             <li>[2018-08-14] (<a href="https://github.com/chamilo/chamilo-lms/commit/eb2483aa43f629a05f0bdd0b81da87a5e27e0e1c">eb2483aa</a>) WYSIWYG: Fix CKEditor bootstrap and chamilo styles loading</li>