cosmetics
change upump_mgr attachment behaviour

Also allow using upipe_set_uri.
take more into account standard deviation

We now take into account three times the standard deviation to be under
1/1000 late packets (considering a Gauss distribution).
take into account decoding time latency
new idempotent module
new functions for attributes comparison
new event to ask for flow def suggestion
new module to autom. transform flow format