Support pretty-print of JSON via HTTP API

[otoolep]

Spot-check unit tests added.

[otoolep]

I find this to be very useful when working directly with the API -- it's much easier on the eyes to be able to get:

$ curl -G 'http://localhost:8086/db/test1/series?u=root&p=root&pretty=true' --data-urlencode "q=select * from hd_used"
[
    {
        "name": "hd_used",
        "columns": [
            "time",
            "sequence_number",
            "host",
            "mount",
            "value"
        ],
        "points": [
            [
                1402627488062,
                50001,
                "serverA",
                "/mnt",
                23.2
            ]
        ]
    }
]
$ curl 'http://localhost:8086/cluster/shards?u=root&p=root&pretty=true'
{
    "longTerm": [],
    "shortTerm": [
        {
            "endTime": 1403136000,
            "id": 1,
            "serverIds": [
                1
            ],
            "startTime": 1402531200
        }
    ]
}

[otoolep]

FWIW -- I do wish I could see a way to configure the output code in few places, but I don't see a clear way. This doesn't seem too bad.

[tisba]

That is a great idea! I'd love to see this being merged. Thanks!

[otoolep]

Any other feedback on this? Go or no-go?

[jvshahid]

Thanks @otoolep. The change is merged into master.