Evan, Jeff, Stefan

Attached is a plot of H1:OMC-READOUT_PREF_OFFSET, H1:OMC-READOUT_ERR_GAIN and H1:OMC-READOUT_X0_OFFSET over the last 10 days.
Notice the significant lock-to-lock fluctuations - they were recalculated every time the interferometer locks.

To avoid having these fake 'optical gain' changes we decided to hard-code
 H1:OMC-READOUT_PREF_OFFSET = 1.3689
 H1:OMC-READOUT_ERR_GAIN    = -8.7614e-7
which are their values during the calibration DARM UGF measurement on 2015/08/30 12:08:43 UTC (GPS 1124971740).
The values are now set in DC_READOUT in the ISC_LOCK guardian. The actual values are in the lscparams file: lscparams.omc_readout_pref and lscparams.omc_readout_err_gain.


Just before NOMINAL_LOW_NOISE we added a new state with code to average the IMC input power for 5 sec and the set
 H1:PSL-POWER_SCALE_OFFSET to the measured power, and 
 H1:OMC-READOUT_X0_OFFSET such that the DCPD values are servoed to lscparams.omc_dcpd_sum_target which currently is 20mA.
(This had been done before, but just based on one ezca read of the IMC input power.)

To avoid being affected by the DC coupled ISS 2nd loop engagement, we moved the ENGAGE_ISS_2nd_LOOP slightly earlier, between COIL_DRIVER and LOWNOISE_ESD_ETMY.