Added normalisation CER and CER lower, clean-ups, simplified conf int…

[Thelukepet]

"Normalised" CER support:

• Added norm_totalcer which calculates the CER after applying the --normalization_file to both the ground truth label and the prediction
• Added norm_totalcer which does the same as the above but also applies lowercase to the ground truth and prediction
• Both metrics are calculated during the prediction phase and the averages are added to the overview after all predictions are completed

Other:

• Simplification of parts of the main function for readability and clearer prints
• calc_95_confidence_interval now only supports a 95% confidence interval as it was not needed to support other confidence intervals yet