Need development for computing non-HST filter absolute flux calibration covariance matrix

[galaxyumi]

Current calculation of absolute flux calibration covariance matrix is only correct for HST filters. For non-HST filters, the BEAST still computes the covariance matrix for any given filters without complaining as long as it has flist[i].transmit information for any given filters. This is just because the current BEAST doesn’t care if a given filter is HST filter or non-HST filter. This is not accurate for non-HST filters.