images-and-archives has landed

[Joshua Root]

As of r77511, port images are now stored as archives (ticket #19458).
Basic operations all work for me. There's a new script run during 'make
install' that converts existing image dirs into archives. It should
theoretically work with the flat registry and convert from direct mode
too, but I haven't tested that yet.

If you find any bugs... please fix them. ;-)

- Josh