no code changes

I dislike -( and -), but without using a different option parser, can't
easily use bare parens.

--and and --or will become more useful once there are more interesting
limits than --exclude

get, drop: Added --auto option, which decides whether to get/drop content
as needed to work toward the configured numcopies.

The problem with bundling it up in optimize was that I then found I wanted
to run an optmize that did not drop files, only got them. Considered adding
a --only-get switch to it, but that seemed wrong. Instead, let's make
existing subcommands optionally smarter.

Note that the only actual difference between drop and drop --auto is that
the latter does not even try to drop a file if it knows of not enough
copies, and does not print any error messages about files it was unable to
drop.

It might be nice to make get avoid asking git for attributes when not in
auto mode. For now it always asks for attributes.

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.

This will allow adding other styles of output.

This takes advantage of the debug logging done by missingh, and I added
my own debug messages for executeFile calls. There are still some other
low-level ways git-annex runs stuff that are not shown by debugging,
but this gets most of it easily.

Clear up short option confusion between --from and --force (-f is now --from, and there is no short option for --force).

Add --fast flag, that can enable less expensive, but also less thurough versions of some commands.

* Add --fast flag, that can enable less expensive, but also less thurough
  versions of some commands.
* fsck: In fast mode, avoid checking checksums.
* unused: In fast mode, just show all existing temp files as unused,
  and avoid expensive scan for other unused content.

Moved away from a map of flags to storing config directly in the AnnexState
structure. Got rid of most accessor functions in Annex.

This allowed supporting multiple --exclude flags.

still not used

This is not yet complete, as it does not allow starting rsync or scp.