Allow enabling/disabling CLI output formatting with an argument

[lkoskela]

While indented JSON output is great for a human, for script-based use a more compact JSON output would generally be better.

For example, asking for --indent the output would be nicely formatted JSON (like before):

$ spdx --indent "GPL-3.0"
# => {
#        "expression": {
#            "license": "GPL-3.0-only"
#        },
#        "errors": []
#    }

...but when asking for --compact output, the JSON would exclude any non-meaningful whitespace for a compact, single-line output.

$ spdx --compact "GPL-3.0"
# => {"expression":{"license":"GPL-3.0-only"},"errors":[]}

For backward compatibility, it'd be better to default to --indent to not break any existing usage.