``extractedsource`` no longer has a ``decl_err_asec`` property, does it?

Also, the above changes the contents of the CSV file so that errors are now in degrees rather than arcsec, I think. That's probably actually more logical, but we should check with anybody who might be relying on the CSV (@AntoniaR & maybe some folks in Soton/Oxon) that it doesn't have a knock-on effect for them.