Functionality:

• Add BayesianNetworkClassifier an sklearn compatible class for fitting and predicting probabilities in a BN.
• Add supervised discretisation strategies using Decision Tree and MDLP algorithms.
• Support receiving a list of inputs for InferenceEngine with a multiprocessing option
• Add utility function to extract Markov blanket from a Bayesian Network

Minor fixes and housekeeping:

• Fix estimator issues with sklearn ("unofficial python 3.9 support", doesn't work with discretiser option)
• Fixes cyclical import of causalnex.plots, as per #106.
• Added manifest files to ensure requirements and licenses are packaged
• Minor bumps in dependency versions, remove prettytable as dependency