Lepton scale factors - final!!

Took several days to sort out this git mess, so please do check this looks ok to you.
I have made the corrections suggested by @kreczko in #123, which I have now closed.
I rebased, (eventually!) with upstream master and with @EmyrClement's hadronEfficiency branch so everything, including the commit history, should be correct and in order now.
You write this here, but I have not seen any code that would guarantee that ( no file => SF =1)
What did I miss?