Ported TMVATransform to TMVA.h

Using MatrixNet as template reference, moved the TMVATransform class into TMVA.h

I have done a rudimentary test and it seems to work.

The idea is to use the class within the MVA functor as it has been done for MatrixNet:

     F.MVA(
            MVAType='TMVA',
            Config={
                'XMLFile': '${PARAMFILESROOT}/data/Hlt2_Radiative_HHgamma.xml',
                'Name': 'BDT',
            },
            Inputs={
                "ipchi2": log(F.BPVIPCHI2(pvs)),
                'ipchi2_min': log(F.BPVIPCHI2(pvs)),
                'gamma_pt': F.PT,
                'm_corrected': F.MASS,
                'vm_corrected': F.MASS,
                'fdchi2': log(F.BPVFDCHI2(pvs)),
                'vtx_chi2': log(F.CHI2),
                'doca': F.BPVFDCHI2(pvs)
            }) > 0.)

The Config key must pass the XMLFile path and the name of the method to be loaded within the file (there might be several methods in a XML file). So far, the inputs must be passed in the same order as the variables are defined in the XML file, careful!

Finally, a list of things that will be addressed

• Check that necessary configuration has been provided. Throw exceptions when it hasn't.
• Check that the output coincides with the one from TMVATransform.
• Allow the input variables to be passed in any order. Deal with by MVA functor
• Deal with spectator variables. TMVA requires to pass them if they are defined. Keep dummy definitions
• Add verbose-triggered output for testing

It addresses #202 (closed) and since it moves TMVATransform.h from MVADictTools to here, it partially addresses Phys!919 (closed)