Minor code modifications

A few minor changes to the code like:
  - Use of dictionary for seconds retrieved per event
  - Change of print order
  - Tidy up the code
  - Replaced get_max and get_min with python max, min

@ktf 
Result to the output is the same apart the print order and print of a headline. Does not affect cmsPerfStripCharts.py. Let me know if you want to have different plots Also here.