Add primary lookup XPATH for Study.identifiers.value for DDI32 && DDI33

Read from /ddi:DDIInstance/s:StudyUnit/r:UserID when @typeOfUserID attribute is "StudyNumber". See https://cmv.cessda.eu/profiles/cdc/ddi-3.2/2.0.0/profile.html and https://cmv.cessda.eu/profiles/cdc/ddi-3.3/2.0.1/profile.html

This will be the primary lookup and excludes all other lookup locations. If this is not found or the condition for @typeOfUserId is not met, then the old behaviour applies.