Zmq app

Hum, i added some questions about this at the end of the pull req, but I guess my point is: If we use unchanged u1db stuff, we should just depend on the u1db package and import them from the u1db module. If we need to modify them, then it is ok to have our own u1db module somewhere in the project, but even in that case we should depend on u1db, import whatever is needed, and extend its functionality, rather than having all u1db suff copied over.