Git commits in Moodle 3.1.x by David Bogner

commit 18937c1577b69ac2508f965ff86a5424b26a80b6
Author: David Bogner <davidbogner@gmail.com>
Date:   Tue, 13 Dec 2016 22:04:13 +0800
Tag:    v3.1.5

MDL-57374 editor: Pasting plain text in Atto removes all styles/classes