linkdef to generate dictionaries

This linkdef contains the pragma declarations needed to generate the
dictionaries allowing to access the collections from PyROOT.
This file is in a separate directory to avoid polluting pwd
with all the files generated automatically by aclic.
ignore files from python and aclic
cutflow class, courtesy of Chase
add DilTrigLogic to linkdef

Also drop the DilTrigLogic::getMCWeight declaration.
This function was never implemented, and now aclic
complains about 'undefined reference to...'
Selector2Lep: enum tauid, define get_* functions

trying to re-implement the selection within a TPySelector.
It turns out I can call all the SusyNtTools functions from
python (see next commit of cutflow_2lep.py), so there's no
need of a TSelector, which just makes things more difficult
to debug. This is just a temporary commit for reference.
working example of cutflow

This cutflow demonstrates that we can use all of the SusyNtTools
functions from python. The yields are roughly the same as the c++
version (need to sort out a small remaining difference)
The execution time is ~2x the one of the c++ equivalent.
implement load_packages()

This is equivalent to the RootCore load_packages.C, but it doesn't
create the annoying file libs.list.