Enable intensity mode observations to be calibrated by polarimetric mode calibration products

The VISP pipeline was created with the expectation (and checks to the effect) of intensity mode data being taken with one modulation state, and all of the calibration products also being taken with one modulation state. This has proven to not be the reality. To increase summit efficiency and stop the need to take extra calibrations when intensity mode is used, the associated calibration products are the polarimetric darks, gains, etc that were taken that day. This is not optimal as we haven not yet proven that intensity mode works when using all intensity mode calibration products and checked that intensity mode observations on the summit work but we need to handle this.

To that end, this PR modifies the tags recorded when parsing the VISP data in intensity mode so that if the observe data is of type observe_intensity, then the modulator state of all frames is 1, no matter what the headers say. This results in the different modulation state data being averaged together which is the intended result.