neuralnetlib 4.1.0

• fix(LSTM): huge improvements in gradient flow
• feat(gradient_norm): better batch handling
• fix(Callbacks): now fully working generically
• fix(metrics): val_loss
• fix(Embedding): bias in output
• fix(display): val_*
• feat(metric): add pearsonr
• feat(metric): add kurtosis
• feat(metric): add skew
• fix(metric): skewness and kurtosis when variance=0
• fix(gan): batch logs
• fix(activation): config loading
• feat(lstm): improved flexibility and parameterizing
• docs(notebook): fresh run
• ci: bump version to 4.1.0