Add noise and x-talk values with variation to obs_lsst based on as measured values.

[cwwalter]

Currently we are using the same noise and x-talk values for all sensors (based on a typical value as measured on the test stands).

[cwwalter]

@jchiang87 @RobertLuptonTheGood Are noise the noise and x-talk now in obs_lsst?

(asked about non-linearity in other issue)

[jchiang87]

X-talk still needs to be measured, I think. There is a JIRA issue for updating gains, read noise, and saturation levels. I think that update should use Run 6 measurements, which were just taken last week, but there is still some optimization to do for running the CCDs.

[cwwalter]

Noise is implemented.

Waiting for data from camera team. Code is implemented.