parameters for serializing a resource should change to be more coherent

[mikaa123]

When adding a representation to a resource, we do:

myResource
    .representation('representation-name', function (e) {
         // heavy work goes there.
    }

In order to be more coherent, we should call the following to get its representation:

myResource('representation-name', entity);

instead of the actual myResource(entity, 'representation-name');