add :include to load o2m or m2m associations of a collection in single extra RPC call

[rvalyi]

see how it's implemented in Rails: http://apidock.com/rails/ActiveRecord/Serialization/to_json the idea is once we have the collection, we do one more OpenERP read request to load the associations for all the records, then we attach them back to the records (via loaded_associations?) thoughts?