Remove copy/clone from fitsfile
Remove copy/clone from fitsfile

This emphasises that a fitsfile must be unique and represents an
open file, which cannot be copied or cloned

mindriot101/rust-fitsio,mindriot101/rust-cfitsio,mindriot101/rust-fitsio,mindriot101/rust-cfitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio