Make the user properties columns in the QTI assessment results file configurable

The csv created when using the archive tool for archiving tests shows instead of the user name the institutionnumber which is a link to the visitingcard of the user.

testing.frentix.com
Laufnummer Name Vorname Benutzername Institutionsnummer Test Punkte Bestanden IP-Adresse Datum Gesamtdauer (s)
1 uibk user1 https://testing.frentix.com/test8/url/Identity/121602048 1.0 true 138.232.11.14 2014-03-21T09:20:29 11 1 0 0 0

UIBK OpenOLAT
"Sequence number Name First name User name Institution identifier Test score Passed IP address Date Total time (s) 1_R1 1_R2 1_R3 1_R4 2_R1 2_R2 2_R3 "
"1 Onestone Alberta https://lbt.uibk.ac.at/url/Identity/8617989 n/a 2.0 true 138.232.11.14 2014-03-21T10:00:45 12 ""1"" ""0"" ""0"" ""0"" ""1"" ""0"" ""0"" "

The solution is to implement a new user properties usage context org.olat.ims.qti.export.QTIExportFormatterCSVType1 for the QTI download file and use a custom user-identifier property that reflects the username.

This issue will implement

1) the new user properties context which can be configured in src/main/java/org/olat/user/propertyhandlers/_spring/userPropertiesContext.xml. Whenever an installation wants to have the user name in this report, the user name must be added as a special user property and configured for this context

2) a new user property UserNameReadOnlyPropertyHandler which can be used to display the username in a read only manner. This new property is configured in the QTI download.