Subscription listener: add max count

[maf-soft]

I have frequently the problem that large messages cannot be retrieved or not more than one. I need this to view and/or delete a certain amount of messages.

Now I noticed the subscription listener feature. It could be (ab?)used for both if it had a max count option, to automatically stop after x messages. That would be easy to do and very helpful.

-> Feature request

Discussion: of course, other issues could also be created from my above need:

• option to delete x messages (instead of only purge all)
• handling of large messages by the "Receive Messages" option
• subscription listener should support receiving from deadletter