Add code for TopAFB analysis

Note there are only a few very minor additions to shared files:
https://github.com/linacre/SingleLepton2012/compare/cmstas:master...master

macros/Core/stopUtils.cc
macros/Core/stopUtils.h
macros/Plotting/PlotUtilities.cc
macros/Plotting/PlotUtilities.h

Everything else is in the new folders:
 ttbar_looper
and
 macros/TopAFBLooper