Update throughput model based on recent measurements and expectation

Based on previous results obtained in laboratories and engineering observations, please update the throughput of instrument. The data file is not only for average throughput but also separated for each spectrograph. Also, please provide the throughput for two cases regarding the VPHG installation direction (the normal direction and 180 deg. rotated direction). Again, since the engineering run on Oct. was canceled, the throughput model is still not based on the real end-to-end measurements.