message: Add StorableResources::empty() convenience function
diff: @@ -73,5 +73,18 @@ struct StorableResources
  resources = { 0, 0, 0, 0 };
  }
  + bool empty()
  + {
  + if(resources[0] > 0 ||
  + resources[1] > 0 ||
  + resources[2] > 0 ||
  + resources[3] > 0)
  + {
  + return false;
  + }
  +
  + return true;
  + }
  +
  std::array<int, 4> resources{ 0 };
  };
  