delete lumi based MEs when the LS processing is over

move LS histo removal in mergeAndResetMEsLuminositySummaryCache

add function markForDeletion to DQMStore

shrink down the markForDeletion function

fix invalid iterator

move markedToDelete and markToDelete to be private in the MonitorElement class

added a comment to the markToDelete method
Merge pull request #5866 from deguio/deleteMEafterWriting_v3_72x

delete lumi based MEs when the LS processing is over