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/ParseUser.spec.js

@@ -2523,7 +2523,7 @@ describe('Parse.User testing', () => {
   });
 
   it_exclude_dbs(['postgres'])('should cleanup null authData keys (regression test for #935)', (done) => {
-    const database = new Config(Parse.applicationId).database;
+    const database = Config.get(Parse.applicationId).database;
     database.create('_User', {
       username: 'user',
       _hashed_password: '$2a$10$8/wZJyEuiEaobBBqzTG.jeY.XSFJd0rzaN//ososvEI4yLqI.4aie',
@@ -2557,7 +2557,7 @@ describe('Parse.User testing', () => {
   });
 
   it_exclude_dbs(['postgres'])('should not serve null authData keys', (done) => {
-    const database = new Config(Parse.applicationId).database;
+    const database = Config.get(Parse.applicationId).database;
     database.create('_User', {
       username: 'user',
       _hashed_password: '$2a$10$8/wZJyEuiEaobBBqzTG.jeY.XSFJd0rzaN//ososvEI4yLqI.4aie',
@@ -2842,7 +2842,7 @@ describe('Parse.User testing', () => {
   });
 
   it('should not create extraneous session tokens', (done) => {
-    const config = new Config(Parse.applicationId);
+    const config = Config.get(Parse.applicationId);
     config.database.loadSchema().then((s) => {
       // Lock down the _User class for creation
       return s.addClassIfNotExists('_User', {}, {create: {}})