rework images JSON
bump api version and ensure backward compat
fix "images -a"
move "images -viz" to client
bring back /images/viz, but 404 for latest
implement "images -tree"
make existing tests pass
adding test for "images -viz"
adding test for "images -tree"
add image size to -tree
update "images" documentation
fixup for rebase
fix /images/json doc for 1.7
updating cli help doc for images
Merge pull request #1794 from justone/add-images-tree

add -tree option to images