Jenne, Sheila, Jeff, Lili

We made a few changes to the pyDARM function actuation.py today.  

1) In the testDCgain calculation, there were two minus signs that canceled each other out, as Jenne pointed out.  there was a -1 for the linearization sign, which was always applied even though we don't use the linearization.  This was canceled by the "attractive" sign, which was due to confusion about the ESD direction.  We've established that when the bias sign is positive, the ESD has the same sign as the osems, so there isn't any need to track another minus sign in addition to the bias sign. We've removed these two signs which were canceling each other out, and edited the comments.  

2)In process_actuation_measurements, there is some code that takes the measurements and divides out the drivealign filter if the excitation point is calexc, or does nothing if the excitation point is test (after drivealign).  This code was also removing the sign of the gain in the drivealign filter, but there was a typo that meant that for the test mass, instead of dividing the gain of the L3 drivealign L2L filter, it was removing the sign of the L2 LOCK filter.  Removing this sign isn't necessary, and if it were done as intended there would be an incorrect sign in the plots.  This bug wasn't noticed since the gain of the L2 LOCK filter happened to be positive.  We have removed the removing of the sign, and simplified the code in this section. 

3) In the plots produced by this code, there are some places where the model/measurement is plotted, and some places where 1-|measurement/model| is plotted, which can cause some confusion about the sign.  Jeff has been changing these to measurement/model slowly, so I have continued to make that change in the actuator fitting plots.