Method getTimeFirst

include/DataSet.h:215–226

      }

      bool getTimeFirst(const KeyType &ID, double& Timestamp) const
      {
        if(this->checkID(ID))
        {
          Timestamp = _DataStreams.at(ID).begin()->first;
          return true;
        }
        else
        {
          return false;
        }
      }

      bool getTimeFirstOverall(double& Timestamp) const
      {