message: Bugfixes in IO_Fileparser: reading a chain.
  The mutex for an appended image must be locked.
  The image index is now fixed so the first image is not ignored.
diff: @@ -119,7 +119,7 @@ namespace Utility
  std::string line = "";
  std::istringstream iss(line);
  std::size_t found;
  - int ispin = 0, iimage = 0, nos = c->images[0]->nos, noi = c->noi;
  + int ispin = 0, iimage = -1, nos = c->images[0]->nos, noi = c->noi;
  while (getline(myfile, line))
  {
  found = line.find("#");
  @@ -128,11 +128,14 @@ namespace Utility
  found = line.find("Image No");
  if (found == std::string::npos) // The line should contain a spin
  {
  + if (iimage < 0) iimage = 0;
  +
  if (iimage >= noi)
  {
  Log(Log_Level::Warning, Log_Sender::IO, "NOI(file) = " + std::to_string(iimage+1) + " > NOI(chain) = " + std::to_string(noi) + ". Appending image " + std::to_string(iimage+1));
  // Copy Image
  auto new_system = std::make_shared<Data::Spin_System>(Data::Spin_System(*c->images[iimage-1]));
  + new_system->Lock();
  // Add to chain
  c->noi++;
  c->images.push_back(new_system);
  