Add usage of embedding matrix biLSTM CV; Gather error examples; Add docu

[sandertan]

Functional changes:

• Pass embedding matrix as parameter during MetaCAT training during cross-validation. I forgot to add this previously, and it significantly increases scores:
• From cross-validation, gather results per example and save them in a new result file, results/bilstm_predictions_cv.csv.gz
• Save scores from cross validation in new result file, results/bilstm_scores_cv.csv.gz
• Add functioning MedCAT config file and run MedCAT in notebook 04_medcat_usage.ipynb with a recent concept database. SARS-CoV-2-infectie is now correctly recognized and linked, and the negation is also correctly identified!

Non-functional changes:

• Add markdown documentation in many notebooks.
• Merge the notebooks that create and evaluate the model based on the whole DCC set.
• Attempt to improve naming and ordering of notebooks.
• Remove everything from README.md that was not used.