copy_section argument order and name

[kbarbary]

copy_section(hdu, dest, range...) has an argument order reversed from the standard order, where the destination is the first argument. This would be easy to switch and deprecate the old version.

Perhaps the name should be copy_section! or just extend Base.copy!. This is slightly different than Base.copy! because dest::FITS and hdu::ImageHDU are not the same types of things.