CGREventWithEeIDs has also been optimized and properly tested. Comments
have been added explaining the process.
When sending a request to AttributeS from EEs, CostDetails from the reply
will now be overwritten by the original CostDetails to preserve its type.
The downside is that we are assuming that CostDetails was not altered by
AttributeS. We might consider adding a type check against *engine.EventCost
to at least stay backwards compatible with *gob and *internal connections.
general_tests/ees_it_test.go has been updated to ensure changes are working
properly.
