PerfExample listener warm up

[timfox]

I notice that a number of warm up messages was added for the sender, but not for the listener.

We need it on the listener too.

Also I suggest number of warmup messages is specified in build.xml not calculate from num messages / 10

[timfox]

We should also allow the ack mode to be specified as an argument to the listener or sender (currently it's hardcoded to DUPS_OK).

We should also allow disabling of the queue drain by a param.

If you just want to measure the consume rate, i.e. send a bunch of messages then after that, consume them, currently it's not possible since it assumes the listener must be started first and all messages drained.