Implementation should be a method that extracts
a key from the supplied {@link FTPClientConfig FTPClientConfig}
parameter and creates an object implementing the
interface FTPFileEntryParser and uses the supplied configuration
to configure it.
Note that this method will generally not be called in scenarios
that call for autodetection of parser type but rather, for situations
where the user knows that the server uses a non-default configuration
and knows what that configuration is.
