Keeping Text.JSON use for now, because it seems a better fit for most of
the commands, which don't use very structured JSON objects, but just output
whatever fields suites them. But this lets Aeson be used when a more
structured data type is available to serialize to JSON.
This includes a generic JSONStream library built on top of Text.JSON
(somewhat hackishly).
It would be possible to stream out a single json document describing
all actions, but it's probably better for consumers if they can expect
one json document per line, so I did it that way instead.
Output from external programs used for transferring files is not
currently hidden when outputting json, which probably makes it not very
useful there. This may be dealt with if there is demand for json
output for --get or --move to be parsable.
The version, status, and find subcommands have hand-crafted output and
don't do json. The whereis subcommand needs to be modified to produce
useful json.
