Tchain

### Allow run on multiple input file

* RootMakePlots now generalises [TTree](http://root.cern.ch/root/html/TTree.html) to [TChain](http://root.cern.ch/root/html/TChain.html) to allow for running on multiple input files
*  RootMakePlots also separates out the output file from the input file (for downward compatibility, output file defaults to inputfile when running on one input file.)
* updated both c++ and python ctypes wrappers
* updated make_plots.py routine