Support JSON CLI output format

[ebyhr]

Fix #867

Example

$ presto --output-format JSON --execute "select * from tpch.sf1.customer limit 2" | jq
[
  {
    "custkey": 37501,
    "name": "Customer#000037501",
    "address": "Ftb6T5ImHuJ",
    "nationkey": 2,
    "phone": "12-397-688-6719",
    "acctbal": -324.85,
    "mktsegment": "HOUSEHOLD",
    "comment": "pending ideas use carefully. express, ironic platelets use among the furiously regular instructions. "
  },
  {
    "custkey": 37502,
    "name": "Customer#000037502",
    "address": "ppCVXCFV,4JJ97IibbcMB5,aPByjYL07vmOLO 3m",
    "nationkey": 18,
    "phone": "28-515-931-4624",
    "acctbal": 5179.2,
    "mktsegment": "BUILDING",
    "comment": "express deposits. pending, regular deposits wake furiously bold deposits. regular "
  }
]

$ presto --output-format JSON --execute "select * from tpch.sf1.customer limit 2" | jq '.[0].name'
"Customer#000112501"

[findepi]

@ebyhr thanks for your PR!

In #867 i outlined possible output layouts (single JSON object vs a stream of JSON objects; i added examples in the issue).
I imagine stream of JSON objects may be easier to process in... a streaming fashion.
What are your thoughts about this?

[ebyhr]

@findepi Hmm.., it's a difficult choice. How about preparing both format e.g., JSON and JSON_STREAM?

[electrum]

I’d keep the shorter option name for the current streaming format.

[ebyhr]

Changed to streaming format using JSON option. I imagined some non-jq cases and thought one json is better at first. However, I agree with the current style now.

[electrum]

It might be simpler and more efficient to use theJsonGenerator API, since you could loop and write the key/value pairs directly.

[ebyhr]

Updated to JsonGenerator API.

[martint]

There's a typo in the commit message: "formt"

[ebyhr]

Oh, sorry fixed.

[ebyhr]

The travis failed by PRODUCT_TESTS_BASIC_ENVIRONMENT=true and this commit looks unrelated.

[electrum]

Merged, thanks!