Please add guide_delta_scale to the agc_guide_offset

The ag is now optionally calculating the scale error from the guiders, and broadcasting that in an MHS keyword.

This should be added to the opdb, and so a new field should be appended to the agc_guide_offsets table.

From watching guider operations I will suggest also adding a column for a mask of the active elements (offset, rotation, focus, scale) which are being fit.