Use a wrapped PDO Statement instead of a custom class for `pdo_sqlsrv` since `PDOSqlsrv\Statement` doesn't extend `PDOStatement` anymore.

[DBAL-2958] Replaced extension of \PDOStatement with a composition to avoid having to replicate the \PDOStatement interface in ResultStatement

HHVM does not allow declaration of interface implementation without
real implementation of methods which parameters differs from parent
class.

- Fixed docblocks
- Removed return statements on void methods
- Cleaned up unused private / local variables
- Fixed license issues
- Removed SVN leftovers
- Fixed doctrine-project.org links
- Added line breaks before return statements

Revertd partially the support to DBAL\Transaction, it was wrong. Fixed implementation of ORM\EntityTransaction and fixed tests.

[2.0] Implemented DQL bulk DELETE support for Class Table Inheritance. Other cleanups, refactorings and docblock additions.