all: Hdu -> HDU. refactor Move{Rel,Abs}Hdu into SeekHDU
file: simplify exposed API
file: make Delete also Close
file: less alloc
rkey: simplify File API
list-head: use simpler API
imlist: print images
column: proper TDIM handling + get name from fits_get_colname
tablist: better error handling
image: first stab at loading images
imlist: add FIXME
all: add image loading for PrimaryHDU too