message: use const std::string& for parameters in Node methods
diff: @@ -141,7 +141,7 @@ namespace ospray {
  std::shared_ptr<sg::Node> node;
  //! return child with name c
  - NodeH& operator[] (std::string c) { return get()->getChild(c); }
  + NodeH& operator[] (const std::string &c) { return get()->getChild(c); }
  //! add child node n to this node
  NodeH operator+= (NodeH n)
  @@ -200,7 +200,7 @@ namespace ospray {
  std::string getDocumentation() { return documentation; }
  - void setDocumentation(std::string s) { documentation = s; }
  + void setDocumentation(const std::string &s) { documentation = s; }
  /*! \brief return bounding box in world coordinates.
  @@ -227,8 +227,7 @@ namespace ospray {
  virtual void setChildrenModified(TimeStamp t)
  {
  - if (t >childrenMTime)
  - {
  + if (t > childrenMTime) {
  childrenMTime = t;
  if (!parent.isNULL())
  parent->setChildrenModified(childrenMTime);
  @@ -236,7 +235,7 @@ namespace ospray {
  }
  //! return named child node
  - NodeH& getChild(std::string name) {
  + NodeH& getChild(const std::string &name) {
  std::lock_guard<std::mutex> lock{mutex};
  if (children.find(name) == children.end())
  std::cout << "couldn't find child! " << name << "\n";
  @@ -244,7 +243,7 @@ namespace ospray {
  }
  //! return named child node
  - NodeH getChildRecursive(std::string name) {
  + NodeH getChildRecursive(const std::string &name) {
  mutex.lock();
  Node* n = this;
  auto f = n->children.find(name);
  @@ -266,7 +265,7 @@ namespace ospray {
  }
  //! return all children of type
  - std::vector<NodeH> getChildrenByType(std::string t)
  + std::vector<NodeH> getChildrenByType(const std::string &t)
  {
  std::lock_guard<std::mutex> lock{mutex};
  std::vector<NodeH> result;
  @@ -285,7 +284,7 @@ namespace ospray {
  }
  //! return child c
  - NodeH& operator[] (std::string c) { return getChild(c);}
  + NodeH& operator[] (const std::string &c) { return getChild(c);}
  //! return the parent node
  NodeH getParent() { return parent; }
  @@ -351,10 +350,10 @@ namespace ospray {
  virtual void postCommit(RenderContext &ctx) {}
  //! name of the node, ie material007. Should be unique among children
  - void setName(std::string v) { name = v; }
  + void setName(const std::string &v) { name = v; }
  //! set type of node, ie Material
  - void setType(std::string v) { type = v; }
  + void setType(const std::string &v) { type = v; }
  //! get name of the node, ie material007
  std::string getName() { return name; }
  