add PrCheckerEfficiencyHandler_HLT2

Dear experts,

We would like to add two option files for making the efficiency plots of HLT2 reconstruction: PrCheckerEfficiencyHandler_HLT2.py and utils/ConfigHistos_HLT2.py.

The PrCheckerEfficiencyHandler_HLT2.py script is written using PrCheckerEfficiencyHandler.py as a reference, and now it has been used locally to produce the efficiency plots. Our target is to make it run automatically in nightly tests (WIP).

PrCheckerEfficiencyHandler_HLT2.py takes the output of PrCheckerEfficiencyPlots_HLT2.py as input, and we propose to add the script PrCheckerEfficiencyPlots_HLT2.py to PRConfig in another MR.

The structure of the handler is written according to README.md, and tested using testHandlers.py.

We would like to send some plots to EOS area, like the existing file PrCheckerEfficiencyHandler.py. But it seems that under the environment of lb-run ROOT python, the command wwwDirEos = os.environ.get("LHCBPR_WWW_EOS") will return nothing. So currently it's set as: wwwDirEos = "/eos/lhcb/user/m/mengzhen/Electron_Efficiency/", and check whether one can get the png plots in this directory.

The exact procedure to run the local test is:

1. Copy the file /eos/lhcb/user/m/mengzhen/Electron_Efficiency/PrCheckerPlots_HLT2.root to a directory where you have access to read and write, labelled as My_directory. This root file is produced by another script, which will be merged into PRConfig master branch soon.
2. Change the eos directory wwwDirEos = "/eos/lhcb/user/m/mengzhen/Electron_Efficiency/" to somewhere you have access to read and write.
3. Run testHandlers.py in the ROOT environment by

lb-run ROOT ./testHandlers.py -r My_directory -l PrCheckerEfficiencyHandler_HLT2 | tee log

Then in the directory where you run the testHandlers.py script, you will be able to see: b405be76-2e0c-11e9-b2dc-fa163ec68ba7.zip, efficiency_hlt2_plots.root, TTrack_seed_eta25_effpt.png, TTrack_seed_eta25_isDecay_effpt.png, and TTrack_seed_eta25_PairProd_effpt.png. And in My_directory, the log file (collect.log) will be generated. The png files will be renamed and copied to the eos area, and for my case, it's in /eos/lhcb/user/m/mengzhen/Electron_Efficiency/efficiency.