Compatibility Update for doctrine/dbal 4

[MaxBoeh]

Thank you for providing this one!

As recent doctrine versions changed some method signatures, I went over this package and adjusted it accordingly.

Handled changes (Doctrine Changelog):

• BC BREAK: Doctrine\DBAL\DBALException class renamed
• BC BREAK: Exception classes have been converted to interfaces
• BC BREAK: Removed DBALException factory methods
• Added method return types to comply with parent signatures
• Renamed method arguments according to their parents
• Fixed spelling of Platform-classes (different casing)

A thing I haven't touched: The class Doctrine\DBAL\Platforms\SQLServer2008Platform was removed with doctrine/dbal version 3.0 (link to changelog). I'm not familiar enough with SQLServer to know if the code branches should be removed or the conditions can be opened to apply on SQLServer in general.

As this MR is full of breaking changes it should lead to a major release.