Created Production class to handle production ntuples

Since ntuple files do not follow MajoRat file naming convention, production
class extracts the relevant parameters from the filename and corresponding
production macro. To create a histogram, the Production objects use the
methods inherited from SpectrumData, except fill_histogram is overridden
by a new method wich gets the ntuple from production data and passes to a
TChain, meaning the energy information can be easily extracted. Since it
also inherits from WriteSpectrum, the generated histogram can be easily
saved to file.

MajoRat's suite of unittest have also been updated to accommodate the new
Production class and some utility modules have been updated.