message: Add max_count option for ModelSpec
diff: @@ -27,6 +27,10 @@ class PassConfig {
  param = m_config.get(name, (Json::Int64)dflt).asInt();
  }
  + void get(const char* name, size_t dflt, size_t& param) const {
  + param = m_config.get(name, (Json::UInt)dflt).asUInt();
  + }
  +
  void get(
  const char* name,
  const std::string& dflt,
  