Adding Gaussian Naive Bayes Algorithm in C++

[m-lin1]

Fixes issue:

Addresses Issue #3706, adding in a C++ version of the Gaussian Naive Bayes algorithm

Changes:

Addition of Gaussian Naive Bayes algorithm for C++ and an additional test file, inputs.csv, that was used in the algorithm. The code should be a basis for the algorithm, but it has some limitations i.e. what kind of input it can take. I believe it should still have the essentials of the algorithm though. The code only outputs the accuracy of the predictions made using Gaussian Naive Bayes.

[aniketmdinde]

Can you please assign me this issue. I would like to work on it.