Migrating HltSusyExoPostProcessor to new dqm interface

This is because, for a change, I wanted to migrate a Harvester as well.

This is only one module:
HLTriggerOffline/SUSYBSM/interface/HltSusyExoPostProcessor

(I skipped HLTriggerOffline/JetMET/interface/JetMETDQMPostProcessor because apparently that one was already done.)