Avoid using abstract objects in parameters and return values

I'm developing the SOAP server for the services module. I've found some design flaws dificulting the servers development.

- Soap requires a definition of the information exchange schema. It's not possible to declare such information when a service expects or returns a std class object. The use of undefined data types can't be handled by the SOAP validator, so it breaks the soap interface at all. It's suggested to use a paired "name" => "value" array that can be handled by any kind of connector instead of using std class objects.

The current "testing" module submitted in http://drupal.org/node/147941#comment-653146 works well but is not able to handle std class objects (In fact, it's the soap interface what is not able to handle that, as it can't be validated against the parameters/return schema).

For the services to be really exportable to any kind of client/server, it's mandatory to support elements not understanding std class objects. The paired array is the best suggestion for that.