Bug 1989388: Allow 'lis_person_sourcedid' to be recorded as a remoteusername

And record it as remoteusername to the parentauth
This is because moodle can send the moodle ID as remoteauth name not
the username from the remote IdP that ties everything together

Also tidy up LTI_Advantage to be like LTI
- See Bug 1943772, commit ec27a6d7

Change-Id: Icbc3bc4511d9cb3b1fb12103f76f5d67539224e3
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>