Refactors configuration management (#4271)

* Adds flow types / Configuration interfaces

* Lets call it options

* Use a single interface to generate the configurations

* Translates options to definitions only if comments are set

* improves logic

* Moves objects around

* Fixes issue affecting logging of circular objects

* fixes undefined env

* Moves all defaults to defaults

* Adds back CLI defaults

* Restored defaults in commander.js

* Merge provided defaults and platform defaults

* Addresses visual nits

* Improves Config.js code

* Adds ability to pass the default value in trailing comments

* Load platform defaults from the definitions file

* proper default values on various options

* Adds ParseServer.start and server.start(options) as quick startup methods

* Moves creating liveQueryServer http into ParseServer.js

* removes dead code

* Adds tests to guarantee we can start a LQ Server from main module

* Fixes incorrect code regading liveQuery init port

* Start a http server for LQ if port is specified

* ensure we dont fail if config.port is not set

* Specify port

* ignore other path skipped in tests

* Adds test for custom middleware setting

* Refactors new Config into Config.get

- Hides AppCache from ParseServer.js, use Config.put which validates

* Extracts controller creation into Controllers/index.js

- This makes the ParseServer init way simpler

* Move serverURL inference into ParseServer

* review nits

spec/RevocableSessionsUpgrade.spec.js

@@ -4,7 +4,7 @@ const rp = require('request-promise');
 const Parse = require('parse/node');
 
 function createUser() {
-  const config = new Config(Parse.applicationId);
+  const config = Config.get(Parse.applicationId);
   const user = {
     objectId: '1234567890',
     username: 'hello',
@@ -29,7 +29,7 @@ describe_only_db('mongo')('revocable sessions', () => {
     });
     user._upgradeToRevocableSession().then((res) => {
       expect(res.getSessionToken().indexOf('r:')).toBe(0);
-      const config = new Config(Parse.applicationId);
+      const config = Config.get(Parse.applicationId);
       // use direct access to the DB to make sure we're not
       // getting the session token stripped
       return config.database.loadSchema().then(schemaController => {