message: fix clang compiler warning, merge qrack docs
diff: @@ -257,7 +257,7 @@ public:
  return ret;
  }
  - virtual std::vector<std::shared_ptr<Observable>> getNonIdentitySubTerms() {
  + std::vector<std::shared_ptr<Observable>> getNonIdentitySubTerms() override {
  std::vector<std::shared_ptr<Observable>> ret;
  for (auto &term : getTerms()) {
  if (term.first != "I") {
  @@ -268,7 +268,7 @@ public:
  return ret;
  }
  - virtual std::shared_ptr<Observable> getIdentitySubTerm() {
  + std::shared_ptr<Observable> getIdentitySubTerm() override {
  for (auto &term : getTerms()) {
  if (term.first == "I") {
  return std::make_shared<PauliOperator>(term.second.ops(),
  