Allow two extensions to answer same call

Maybe like this:
- boss has his own queue
- incoming call goes to another queue, which the conf room and the boss's queue are members of (if possible), that has 'queue no answer' on
- conf room issues 2 new calls (if it does work like that) directed to another queue, which the boss's queue and the assistant extension are members of, and also has queue-no-answer set; Replace conf room with maybe a custom application or custom destination, if appropriate.
- if the assistant picks up, the call is set to 'taken' by the second queue, and boss's phone keeps ringing after a short gap, thanks to the conf room (maybe with a cid remark, to say 'through assistant')
- if boss picks up first, the incoming queue cancels the call to the conf room and hence to the assistant,
- hope this woks as imagined.