feat(client/js/*/uploader.basic.js): #1252 - Allow to change successEndpoint per upload

I implemented the feature request #1252. I basically cloned the *uploadSuccessParams* behavior, as indicated by @fschwahn in his comment. This code was tested with S3, but **not with azure**.

To change the uploadSuccess endpoint, simply call this method with the new endpoint and the file ID:
```javascript
myUploader.setUploadSuccessEndpoint("YOUR ENDPOINT", id);
```