Import branches/dev/proof r20306

  Summary (see branch logs for more details):

  - Set of changes related to CPU quota control including
    - broadcast of centrally determined priorities
    - mechanism to renice processes in a quantitative way
  - New packetizer for non-tree based analysis and related API in TProof (from L. Tran-Thanh)
  - Support for merging output objects saved in files on the workers (from L. Tran-Thanh and me)
  - Improve version binary compatibility checks using also the SVN revision number
   (when available) to define the running version.
  - Extend the version binary compatibility checks also to the cached selector binaries.
  - Extend TDSet::Lookup so that in case of missing files, it can remove them from the
    dataset (option removeMissing must be set).
  - Move the data set lookup to the TProofPlayerRemote::Process.
  - Handle properly the case of incomple datasets: if the file is not found in the lookup
    don't try to validate it; add it, instead, to a 'missingFiles' list returned in the
    output list (fixing bug #28800 in Savannah).


git-svn-id: http://root.cern.ch/svn/root/trunk@20307 27541ba8-7e3a-0410-8455-c3a389f83636