Allow rotation of "Session Log" and "Changes Log"

Plan:

1. add "SessionLogRotationInterval" system setting (label: "Keep "Session Log" for") to the "Logs Settings" sub-section in the "Configuration > Website > Advanced" section with following options: "1 day", "1 week", "2 weeks", "1 month", "3 months", "1 year", "2 years", "3 years", "5 years", "Forever (never deleted automatically)"
2. create "session-log:OnRotate" scheduled task (see "email-log:OnRotate" for example) to cleanup logs
3. don't session logs of active sessions
4. before deleting "session log" delete all "changes log" records associated with that "session log"
5. add protection against removing more than 100 records per run (to avoid "out of memory" error)
6. run event once per day