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/Options/parsers.js

@@ -0,0 +1,75 @@
+function numberParser(key) {
+  return function(opt) {
+    const intOpt = parseInt(opt);
+    if (!Number.isInteger(intOpt)) {
+      throw new Error(`Key ${key} has invalid value ${opt}`);
+    }
+    return intOpt;
+  }
+}
+
+function numberOrBoolParser(key) {
+  return function(opt) {
+    if (typeof opt === 'boolean') {
+      return opt;
+    }
+    if (opt === 'true') {
+      return true;
+    }
+    if (opt === 'false') {
+      return false;
+    }
+    return numberParser(key)(opt);
+  }
+}
+
+function objectParser(opt) {
+  if (typeof opt == 'object') {
+    return opt;
+  }
+  return JSON.parse(opt)
+}
+
+function arrayParser(opt) {
+  if (Array.isArray(opt)) {
+    return opt;
+  } else if (typeof opt === 'string') {
+    return opt.split(',');
+  } else {
+    throw new Error(`${opt} should be a comma separated string or an array`);
+  }
+}
+
+function moduleOrObjectParser(opt) {
+  if (typeof opt == 'object')  {
+    return opt;
+  }
+  try {
+    return JSON.parse(opt);
+  } catch(e) { /* */ }
+  return opt;
+}
+
+function booleanParser(opt) {
+  if (opt == true || opt == 'true' || opt == '1') {
+    return true;
+  }
+  return false;
+}
+
+function nullParser(opt) {
+  if (opt == 'null') {
+    return null;
+  }
+  return opt;
+}
+
+module.exports = {
+  numberParser,
+  numberOrBoolParser,
+  nullParser,
+  booleanParser,
+  moduleOrObjectParser,
+  arrayParser,
+  objectParser
+};