Handle metadata based serialisation in apiv3 basic_create_fallover

Per CRM-13123 there is now a standard for describing how fields should be serialised using metadata. I think this should be exposed using basic_create fallover (maybe more later) for api v3. This can be easily handled in 'copyValues' but I think it should be by an extra param $serializeArrays so we can trigger it from only one place initially (to prevent unexpected consequences)

Encouraging extension writers to add the metadata to support this should also be good for them transitioning to api v4.