Update the configuration of the FastTimerService used for Offline DQM

  - read the default configuration for the Service and Cliebnt from the
    _cfi files, instead of defining the modules from scracth
  - add a module to set the event luminosity
I have add the `dqmFastTimerServiceLuminosity` module only to the DQMOfflineCommon sequence, but you should make sure that it is always run for all events, otherwise the FastTimerService will not have the instantaneous luminosity for the event.