Optionally add a bias between exposures from {{startExposures}}

The iic startExposures exptime=S command starts an unbounded sequence of scienceObject exposures.

While the red shutter is out, we need biases bracketing each scienceObject. One at the start, one between each exposure, and one at the end.

Well, in many cases it will make little sense to have an ending bias. I'm not sure what to say about that. Add a optional noSunssBias to finishExposure? I think we will know when it is not worth trying.