NNTPGrab

It should be possible that NNTPGrab can be used by multiple users at the same time.
This means that each user can add their own downloads to the queue and all queued files
get downloaded from the same server(s). This can be useful for environments where an usenet
account is shared between multiple users which are using the same internet connection.
In the current situation users have to wait on each other because of connection limits set
by usenet providers (like only 3 simultaneous connections to a server)