D3Upload: Validate and process files uploaded via Web forms

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

It can take the name of a given file upload input and check if a valid file was uploaded and can be processed.

It checks whether the file has a valid name extension. It also checks whether a given destination directory exists and is writable.

If all is well, the class copy the file to destination directory, optionally with an unique file name.

The code and comments are in Turkish.