TTH/Susy updates

refactored susy configuration, as discussed at a coffee meeting last week:
- new lepton analyzer that only select leptons, without applying cuts
- susy core cfg and core tree producer (that serve as templates), and an implementation for susy multilepton

also includes:
- auto-handle with fallback, so that one can run transparently on V5_18 and earlier samples without having to change the input label of the vertex collection
- fix in the "electronID(xxx)" method of the cmg::Lepton for cut-based IDs, and have lepton id functions return true if an empty string is passed (so that one can make the id configurable)
- improve the multiloop alias from #46
- other improvements to the python plotting tools