smurf: Merged CSO fits from 2012 August

The original 2013 March and April fits are removed as they do not
include RMS values and so are not recognized as valid lines.
smurf: cso2filt is now implemented as two separate functions

This routine was inefficient when called from a loop many times
because it read the header and extracted values from keymaps
each time. smf_cso2filt_tau is now refactored to call one
routine to get the conversion coefficients and another routine
to apply them.
smurf: Calculate filter extinction coefficients outside loop

30% of the routine was spent scanning FITS headers and extracting
identical coefficients from the KeyMap. Now do this once outside
the loop and apply the coefficients.