Allow QFile.copy() method to overwrite file by having allow_overwrite argument

I suggest a parameter named allow_overwrite be added to the instance method and also to the static method of QFile.

So, a developer could then do...

QFile.copy("path/source_file.extension", "path/target_file.extension", allow_overwrite=True)

or

file_manager = QFile("path/source_file.extension")

file_manager.copy("path/target_file.extension", allow_overwrite=True)

It's cumbersome that if we need to overwrite a file, we must remove the target file - if it exists by checking with QFile.exists("path/target_file.extension") - and then do a copy. For large files or files from the Internet, this introduces an overhead.