Add the possibility to save the perfomance information shown by the dialog into a small
   ntuple included in the output list. The ntuple contains 5 floats (processing time, number
   of active workers, event rate, MBytes read, number of effective sessions on the cluster)
   and it is filled each time the number of active workers changes or at max 100 regular
   intervals at least 5 secs apart; in this way the ntuple has at most O(100 entries + number
   of workers).
   To enable the saving of the ntuple execute the following:
               proof->SetParameter("PROOF_SaveProgressPerf", "yes");
   before running the query. The ntuple is called 'PROOF_ProgressPerfNtuple'.

   This patch also adds to the output list the parameters used by the active packetizer. Some
   parameters of general interest (currently MinPacketTime and MaxPacketTime) have been moved
   to TVirtualPacketizer and are always added to the list. Each packetizer is then responsible
   of adding its relevant specific parameter to the dedicated list. The dedicated list is hosted
   in TVirtualPacketizer and is transferred to the output list by TProofPlayer when finalising
   the output list at the end of the query.


git-svn-id: http://root.cern.ch/svn/root/trunk@34748 27541ba8-7e3a-0410-8455-c3a389f83636