Make users aware of security page by adding a SECURITY.md in root.
Clarify safe parts of the API in more detail.
Fix typo and formatting in security docs
Merge pull request #531 from aboks/patch-1

Fix typo and formatting in security docs
Original PDOException is preserved and wrapped by Doctrine\DBAL\Driver\PDOException
Merge pull request #534 from fprochazka/preserve-original-pdo-exception

[DBAL-813] Original PDOException is preserved