Fits_save_fit stores the systematic errors now in form of a string using

the function sys_err_array2string.

This might commit breaks the backwards-compatibility of fits_save_fit,
but was a necessary change. Moreover a bug in the sys_err_array2string-
Routine itself was fixed.

	modified:   src/FITS/fits_save_fit/fits_save_fit.sl
	modified:   src/data/sys_err_array2string.sl