message: Enables getObservable to access Observable as Service
diff: @@ -29,6 +29,9 @@ std::shared_ptr<Observable> getObservable(const std::string type,
  return representation.empty()
  ? std::make_shared<FermionOperator>()
  : std::make_shared<FermionOperator>(representation);
  + } else if (xacc::hasService<Observable>(type)) {
  + auto obs = xacc::getService<Observable>(type);
  + return obs;
  } else {
  if (xacc::hasContributedService<Observable>(type)) {
  auto obs = xacc::getContributedService<Observable>(type);
  