Updating the default cluster collections to PF

This pull request updates the ECAL DQM modules that run over the cluster collections to have the particleFlowClusters as the default source.
The source name is only changed for pp configurations. For HI and cosmics, the original files are kept in
DQMOffline/Ecal/python/ecal_dqm_source_offline_{cosmics|HI}_cff.py

The customizer provided by the Egamma group (RecoEgamma/Configuration/python/customizeOldEGReco.py, in #1834) has the function _customize_DQM, which is empty in the PR. The implementation of the exists but is not included in any PR yet.