CORE-6040 added new error code for internal error
CORE-6040 converted donkey filesystem/download endpoint

It now uses the data-info cart endpoint.
CORE-6040 converted donkey filesystem/download-contents endpoint

It now uses the data-info cart endpoint.
CORE-6040 converted donkey filesystem/upload endpoint

It now uses the data-info cart endpoint.
CORE-6040 converted donkey filesystem/display-download endpoint

It now uses the data-info entries/path/<zone>/<path-in-zone> endpoint.
CORE-6040 removed INTERNAL ERROR code
CORE-6040 switch to using clj-http error trapping
CORE-6040 renamed updown ns to cart
CORE-6040 added query parameter validators