JSON File Upload: Validate and process files uploaded via Web forms

This class can be used validate and process files uploaded via Web forms.

The class can perform several types of validation, like: check whether the user computer IP address is not in a list of banned addresses, check the file size against a given limit, check whether the file name has one of the accepted extensions and check whether file with the same name was previously uploaded.

After validating the file, the class can move it to a given upload folder and add an entry in a log file that records information about uploaded files.

The example demonstrates how to display an updated list of files stored in the upload folder.