Allow settings_schema.json to be divided into multiple files

[t-kelly]

Problem

settings_schema.json is used to defined global settings for an entire theme. It can grow to be pretty pretty large (~600 lines in Narrative), and hard to manage.

Solution

I propose we allow settings_schema.json to be broken up into multiple files so that it can be managed easier. The most straight-forward way of doing this would be to generate a settings_schema.json file from a settings_schema.js file. This file could look something like:

src/config/settings_schema.js

import info from './info';
import typography from './typography';
import colors from './colors';
import social from './social';

export default [
  info,
  colors,
  typography,
  social
];