Fix syntax and make a few tweaks to Alexey's DR

Made the following changes:
    * Moves the cut value to the top of the file as NT_DR_
    * Rename variables to better explain what they do
    * Enforce the use of {}, even for single lines
    * Use deltaR instead of a custom solution
    * Remove cout

Also fixed the position of InitTrigger(), which was accidentally reverted
in the commit.
Add Truth values to pt ratio plot
Add unweighted_counter_ for MC normalization
Add ZSkimmer

ZSkimmer is a filter that selects events with at least two electrons.
The following pairs of electrons satisfy the filter:
    * 15 pt GSF + 10 pt GSF
    * 10 pt GSF + 10 pt NT
    * 10 pt GSF + 10 pt HF
Update cross checker with new colors and phi* bins

Added in the ATLAS binning for Phi*, and added more color/fill
combinations to the plots.

Change the input format from using the directory to using the full
directory and histogram name.

Update the make_plots.cpp file to include the new backgrounds.
Add crab and multicrab configurations for MC

These files are designed for running at Fermi Lab on their local
condor cluster.
Update the rest of the MC in make_plots.cpp
Clean up unused code in zskimmer.py
Add JSON file for filtering events in zskimmer
Remove unused plots from Cross Check Plotter
Add option to set LogX in Cross Check Plotter
Change how BG plots are named in Cross Check Plot

Backgrounds are now named using the name variable in the Dataconfig,
instead of using the key string used in their map. This allows us to
give them a human readable name on the plot while ordering them using a
machine readable key string.

Additionally adjust colors and hatching to remove horizontal stripes.
Minor plotting adjustments in Cross Check Plotter

Adjust the size of the legend.

Change the range of the ratio window.

Add a final Phi* bin.
Begin writing documentation for ZFinder in total

The bare bones are now documented, but more work is still needed.
Adding Single Electron Skim file lists

The skims are of the SingleElectron datasets looking for a pt>15 GSF
electron and a GSF, HF, or Photon (in the photon case with 2.4 < Eta <
3) with pt>10.

These files produce the exact same result as the unskimmed files for the
central region when using ZFinder.
Add Single Electron 2012C/D file lists

These files are not stored locally; they are for use via xrootd.
Rename the skimmer to avoid name conflicts

Data can only be processed by modules with identical names once, so
ZSkimmer is now getting a proper process name that is unique from the
rest of ZFinder.
Re-committing Alexey's changes on top of updated UMN ZFinder. (It was, unfortunately, not possible to separate changes made for Nicole from gen-matching.)