Todd Gamblin 1a1f5674df command: add spack find --json ...

This is another machine-readable version of `spack find`.  Supplying the
`--json` argument causes specs to be written out as json records,
easily filered with tools like jq.

e.g.:

    $ spack find --json python | jq -C ".[] | { name, version } "
    [
      {
        "name": "python",
        "version": "2.7.16"
      },
      {
        "name": "bzip2",
        "version": "1.0.8"
      }
    ]

2019-09-02 19:24:48 -07:00

..

spack

command: add spack find --json

2019-09-02 19:24:48 -07:00