Git merges in Moodle 3.1.15 by Eloy Lafuente (stronk7)

commit f058de06a39da5b48534b31569a0efbc135dbcf5
Author: Eloy Lafuente (stronk7) <stronk7@moodle.org>
Date:   Sat, 10 Nov 2018 19:53:05 +0800
Tag:    v3.1.15

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

commit 513e8044c3b256377345b4055b36a63da48b9b47
Author: Eloy Lafuente (stronk7) <stronk7@moodle.org>
Date:   Tue, 16 Oct 2018 22:05:19 +0800
Tag:    v3.1.15

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