LDEV-3614: Improve processing of Gate activities.
Alter lams_activity_learners table so it reflects its real purpose: storing learners who are allowed to pass a gate.
Find out who is waiting in front of a gate using learner progress (activity attempt).
For sync gate take into account all possible lesson learners (lesson class) rather than only ones who started a lesson.
Use an entity in JSP generation rather than a DTO which is just a wrapper for the entity.
Code clean up.