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/PushWorker.spec.js

@@ -16,7 +16,7 @@ describe('PushWorker', () => {
         }
       }
     }).then(() => {
-      expect(new Config('test').pushWorker).toBeUndefined();
+      expect(Config.get('test').pushWorker).toBeUndefined();
       new PushWorker({
         send: (body, installations) => {
           expect(installations.length <= batchSize).toBe(true);
@@ -161,7 +161,7 @@ describe('PushWorker', () => {
 
   describe('pushStatus', () => {
     it('should remove invalid installations', (done) => {
-      const config = new Config('test');
+      const config = Config.get('test');
       const handler = pushStatusHandler(config);
       const spy = spyOn(config.database, "update").and.callFake(() => {
         return Promise.resolve();
@@ -244,7 +244,7 @@ describe('PushWorker', () => {
     });
 
     it('tracks push status per UTC offsets', (done) => {
-      const config = new Config('test');
+      const config = Config.get('test');
       const handler = pushStatusHandler(config);
       const spy = spyOn(rest, "update").and.callThrough();
       const UTCOffset = 1;
@@ -320,7 +320,7 @@ describe('PushWorker', () => {
     });
 
     it('tracks push status per UTC offsets with negative offsets', (done) => {
-      const config = new Config('test');
+      const config = Config.get('test');
       const handler = pushStatusHandler(config);
       const spy = spyOn(rest, "update").and.callThrough();
       const UTCOffset = -6;