Git commits in Moodle 3.6.x by David Balch

commit 0df5a25aca44e72b4af4df1d2a07b30a000a111a
Author: David Balch <david.balch@conted.ox.ac.uk>
Date:   Mon, 08 Apr 2019 22:36:31 +0800
Tag:    v3.6.4

MDL-65299 Boost: Allow default.scss theme-colors override.


commit 528060a1a968b640447eac128030a8ba60816dd6
Author: David Balch <david.balch@conted.ox.ac.uk>
Date:   Mon, 28 May 2018 12:42:16 +0800
Tag:    v3.6.0-beta

MDL-57742 core_lib: Make tool_consumer_instance_guid optional