Replace Connection with DBAL

[mvorisek]

I would highly prefer to drop all Connection classes in advance to DBAL. This will not solve only the registry, but it would allow to share that connection with Doctrine ORM much easier later.

How Doctrine setup connection?
doc - https://www.doctrine-project.org/projects/doctrine-orm/en/2.7/tutorials/getting-started.html#obtaining-the-entitymanager
which refer to https://github.com/doctrine/orm/blob/1ab9d0b1942a6b70d01640d51056a71916255ecf/lib/Doctrine/ORM/EntityManager.php#L825
which calls https://github.com/doctrine/orm/blob/2a98a98cd36e5eb54ad5ff8ca26fc3a30d5a82ff/lib/Doctrine/ORM/EntityManager.php#L842
which calls a few lines later https://github.com/doctrine/orm/blob/2a98a98cd36e5eb54ad5ff8ca26fc3a30d5a82ff/lib/Doctrine/ORM/EntityManager.php#L845
DriverManager is part of DBAL.