Fixes 3076: clean EventLog and add ModificationId in event API
Issue #3076: add modificationId in eventLog
Ref #3076 : Add canRollback property
Merge pull request #2 from VinceMacBuche/ust_3002/dev/3076_move_eventlog_in_rudder

Fixes #3002 : Change event log to be able to have a rollback system based on them