Git merges in Moodle 3.1.x by Sara Arjona

commit 7a37b0a5a4dd66e419ac383a3d2398c700ebe3bf
Author: Sara Arjona <sara@moodle.com>
Date:   Fri, 11 Jan 2019 00:51:36 +0800
Tag:    v3.1.16

Merge branch 'install_31_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_31_STABLE