Add bullet gem for monitoring query problems
Refactor plis_after method to accept only point line item instace as argument
Refactor plis_after method to accept only single point line item instance
Add caching to plis_up_to and plis_after
correct the bug in add_to_id_list and refactor expire_source to use filtered plis list
change returning result from plis_after and plis_up_to to array instead of activerelation
Refactor expire_source method to use only cached values
Remove Rails.cache.clear command from flush_cahches method
Correct the method naming and get rid of reduntant arguments passed
Factor out ids array populating functionality from  expired_id_list method into separate metjods