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

src/index.js

@@ -9,14 +9,16 @@ import * as TestUtils       from './TestUtils';
 import { useExternal }      from './deprecated';
 import { getLogger }        from './logger';
 import { PushWorker }       from './Push/PushWorker';
+import { ParseServerOptions }    from './Options';
 
 // Factory function
-const _ParseServer = function(options) {
+const _ParseServer = function(options: ParseServerOptions) {
   const server = new ParseServer(options);
   return server.app;
 }
 // Mount the create liveQueryServer
 _ParseServer.createLiveQueryServer = ParseServer.createLiveQueryServer;
+_ParseServer.start = ParseServer.start;
 
 const GCSAdapter = useExternal('GCSAdapter', 'parse-server-gcs-adapter');