message: Add StorableResources::operator-=()
diff: @@ -37,6 +37,12 @@ struct StorableResources
  return out;
  }
  + StorableResources& operator-=(const StorableResources& other)
  + {
  + *this = *this - other;
  + return *this;
  + }
  +
  bool operator<=(const StorableResources& other) const
  {
  return resources[0] <= other.resources[0] &&
  