[4.0] Deprecated class attribute

[rdeutz]

Pull Request for Issue #254

Summary of Changes

In Meeting 106 of the maintainers team the team decided to remove the class parameter from loadObject, loadObjectList and DatabaseIterator.

This way (ussing a custom class as result) of fetching data is not supported over all database drivers so it can lead to problems in the development and using the database package.

Testing Instructions

No tests possible it is ony documenting that the parameter is deprecated and will be removed with version 6 of the package.

Documentation Changes Required

No changes needed it is so widly used that it wasn't part of the documentation ;-)

[HLeithner]

I think this should trigger an custom deprecation message if the input is not \stdClass, since no IDE or analyser understands parameter deprecation.