New python tool to create a sorted event collection

This is event sorter as requested for RDO premixing - to read events in the LumiBlock order

To use it in a transform, add --poestExec step like this:

from CollectionUtilities.SortedCollectionCreator import *
sorter = SortedCollectionCreator(name="SortEvents")
sorter.execute(runArgs.inputRDOFile, outputCollection="sortedRDORefs", sortAttribute="LumiBlockN")

ServiceMgr.EventSelector.InputCollections = ["sortedRDORefs.root"]
ServiceMgr.EventSelector.CollectionType = "ExplicitROOT"