Python Tutorials for CNN, Higgs and RNN added in Tutorials/TMVA

[Neel-Shah-29]

This Pull request: Adds the Python Tutorials to several C files in Tutorials/TMVA.

One of the tasks of Pythonization project for Gsoc was to add Python tutorials for C files in Tutorials/TMVA.
I have added python tutorials for TMVA_Higgs_Classification.C , TMVA_CNN_Classification.C and TMVA_RNN_Classification.C.
The notebooks for the same can be found here.
We can also make an improvement regarding adding a PyTorch model for RNN and train it, its implementation can be found here. We can add this improvement once reviewed.

Checklist:

• tested changes locally
• updated the docs (if necessary)

[phsft-bot]

Can one of the admins verify this patch?

[lgtm-com]

This pull request introduces 20 alerts when merging 8cd3b57 into 7e709f8 - view on LGTM.com

new alerts:

• 6 for Unused import
• 5 for Unreachable code
• 4 for Testing equality to None
• 3 for Module is imported with 'import' and 'import from'
• 2 for Variable defined multiple times

[lmoneta]

We should pass the tutorial options from command line of by defining a function with parameters.
All 3 tutorials should also include PyTorch and Keras and have a way to detect if PyTorch and Keras are installed or not. If they are not installed the corresponding method should not be run. This would avoid adding a veto for the tutorials in the CMake file in tutorials.

[lmoneta]

We could use a more Pythonic way to pass the option to the tutorial. Maybe some command line argument ?