Move transform acl (#2021)

* Move ACL transforming into Parse Server

For the database adapters, it will be more performant and easier to work with _rperm and _wperm than with the ACL object. This way we can type it as an array and so on, and once we have stronger validations in Parse Server, we can type it as an array containing strings of length < x, which will be much much better in sql databases.

* Use destructuring

spec/MongoStorageAdapter.spec.js

@@ -54,7 +54,7 @@ describe('MongoStorageAdapter', () => {
     .then(results => {
       expect(results.length).toEqual(1);
       var obj = results[0];
-      expect(typeof obj._id).toEqual('string');
+      expect(obj._id).toEqual('abcde');
       expect(obj.objectId).toBeUndefined();
       done();
     });