3SS Sync File: Update a local file retrieved from a remote server

This class can be used to create or update local copies of files taken from a remote server.

The class checks whether the local copy of a file already exists. If it does not exist, the file is copied from the remote server.

If the local copy already exists, it compares the remote file and local copy contents. If the contents of the files are different, the class makes a backup copy of the local file and copies the remote file to the local file.