Add multibox pop behaviour

[mrutid]

Provide a BOX array to obtain messages

Several scenarios may apply:

(MUST) Non blocking: get all messages and return

(thinkTank) 1xBlocking: get all messages and return, if no messages are present block till one is present
(thinkTank) AllxBLocking: block till every box has messages

[mrutid]

The final behaviour will be an extension to the current priority queues implementation, extending it by accepting any number of queues.

The algorithm will be implemented as a LUA script in REDIS.
The current priority algorithm / behaviour get override by this functionality (and will disappear)
The Redis cluster for queues will disappear also, so we will rely un Redis cluster when necessary.