Add tests for user_sets and user_set versioning

[pstaabp]

This adds tests (both perl and jest) for user_sets and set versioning. A few changes have been made as well:

• on routes in which course_user_id was used, user_id is used instead for easier handling of permissions mostly related to those with self_access.
• there is a route for user_set for get, put, delete that includes the set_version as well, since this is needed for uniqueness.
• there are routes kept without set_version that will default to set_version => 0

This depends on #112