Support for a config.json - app writable (mutable) and persistent across app launches

[brandonscript]

$session should become ephemeral across app launches, we will create a new property ($settings? or $config?) for persistent settings. During development mode, these settings would be saved to a local .json file, handy for debugging (developer could edit properties in the json file at will); release would not have this, and would instead store them in NSUserDefaults.