For UTF-8: SQLSTATE[HY000] [2019] Unknown character set

A configuration instance is not strictly required by [DriverManager::getConnection](https://github.com/doctrine/dbal/blob/master/lib/Doctrine/DBAL/DriverManager.php#L139).

As an upside, it doesn't add an extra warning for people that use Psalm/PHPmd when starting off from the documentation example. As the Configuration class has an `@internal` block those tools threat it as the other meaning for `@internal`, as in class that is [internal to the library and not for public use](https://docs.phpdoc.org/references/phpdoc/tags/internal.html).

revert back MariaDb1027Platform

Fixes #3121

Conflicts:
	docs/en/index.rst

See discussion at https://github.com/doctrine/doctrine2/issues/7187

It seems to be the case in the rest of this document.

Fixes #2760

One class missed and one non-existing in example at "Supporting Other Databases" page.

At lest it looks like one to me.

Closes #1882

The oci8 driver can connect using oci_pconnect to make persistent connections. Doctrine has support for this if the persistent boolean value is set to true in the documentation. However, this information was not documented.