Introduces flow types for storage (#4349)

* Introduces flow types for storage

* Better typing of QueryOptions

* Adds flow types to SchemaCOntroller,

- runs flow on pre tests
- fixes flow

* Adds ClassLevelPermissions type

* Moves Controller types into a single file

* Changes import styles

* Changes import styles

* fixing method setIndexesWithSchemaFormat (#4454)

Fixing invalid database code in method `setIndexesWithSchemaFormat`:

* It must be a transaction, not a task, as it executes multiple database changes
* It should contain the initial queries inside the transaction, providing the context, not outside it;
* Replaced the code with the ES6 Generator notation
* Removing the use of batch, as the value of the result promise is irrelevant, only success/failure that matters

* nits

* Fixes tests, improves flow typing

spec/ParsePolygon.spec.js

@@ -1,5 +1,5 @@
 const TestObject = Parse.Object.extend('TestObject');
-const MongoStorageAdapter = require('../src/Adapters/Storage/Mongo/MongoStorageAdapter');
+import MongoStorageAdapter from '../src/Adapters/Storage/Mongo/MongoStorageAdapter';
 const mongoURI = 'mongodb://localhost:27017/parseServerMongoAdapterTestDatabase';
 const rp = require('request-promise');
 const defaultHeaders = {