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:

> 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