Consolidate JSON formatting

Summary: In some places `{"foo" : "bar"}` is used, whilst in other places `{"foo": "bar"}` is used, This diff attempts to consolidate these differences and adopt a more standard JSON format.

Test Plan:
```lang=php
> print_r(id(new PhutilJSON())->encodeFormatted(array('foo' => 'bar')));
{
  "foo": "bar"
}
```

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11085