* pr/1615:
Force start session if SSO is used
Improve and simplify session status detection
Improve handling of session variables related to validator
Start session automatically if an addon uses the session and exits
If cache-friendly behavior is enabled, don't skip updateReadedCount()
If cache-friendly behavior is enabled, don't update session when reading document or comment
Add option to enable/disable cache-friendly behavior
Improve the setCacheControl() method
Context::setCacheControl() method added etc.
do not always set mobile/user-agent cookies
선택적 세션 시작 + 서드파티 자료 호환성 (Proof of Concept)