ENHANCEMENT: Lookup of module to record tracking against.

[lushonline]

The current implementation makes assumption that the COURSE has the xAPI OBJECT ID as Moodle IDNUMBER, and there is only one COURSE with that Moodle IDNUMBER.

It also assumes that their is only one Activity (Course Module) in the course with that ID as well.

This is the case if content loaded using the bulk tool.

The processing logic starting around https://github.com/lushonline/moodle-mod_externalcontent/blob/master/lrs/xapihelper.php#L79 though should be updated to:

1. Lookup the COURSE MODULES ($cm) with the xAPI OBJECT ID
2. For each $CM determine the COURSE ($course) and then process the completion