Enhancements

#343 set seed in Optuna
#344 set eval_metric directly in all algorithms
#350 add estimated train time in Optuna mode
#342 add optuna_verbose param in AutoML()
#354 add KNN in Optuna
#356 and Neural Network in Optuna
#357, #348 use mljar wrapper for Random Forest and Extra Trees
#358 add extra_tree param in LightGBM
#359 switch off feature engineering in Optuna mode - only highly tuned models are produced
#361 list all eval_metric in error message
#362 add accuracy eval_metric
#340 support for r2

Bug fixes