Git merges in Moodle 3.1.17 by Sara Arjona

commit f48bea7df85884fc03d0a59860d7fcf6dfb71ba1
Author: Sara Arjona <sara@moodle.com>
Date:   Fri, 08 Mar 2019 18:03:01 +0800
Tag:    v3.1.17

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