Enhancements of TProofPerfAnalysis

  Add new functions (FileRatePlot, FileProcPlot, PrintFileInfo) to extract the information
  per processed file.
  In RatePlot, add possibility to plot the total instantaneous and average rate.
  Add function Summery to show a summary of the query with a comptact frm option convenient
  for saving in text files.
  Documentation at http://root.cern.ch/drupal/content/analysing-performance-tree being updated.