Lepton scale factors

This is the (mostly) finished update to read 7TeV electron scale factors from histogram files.
Compiles and runs, but during running there are some warnings of memory leaks related to TEfficiency, which I was unable to solve...hence WIP.
Also, will remove the couts once this is ready to merge.
OK, two things:
 - why do you need to store (copy the pointer) of a global histogram for every electron for every event?
 - why doesn't the private variable end with '_'?