Compute metrics during evaluation, not during training

[FrancescoCasalegno]

Context

Currently we are computing all metrics during the model training. This is true both for:

• Training of TMD and DL classifiers:
  

  morphoclass/src/morphoclass/console/cmd_train.py

  Lines 139 to 141 in 35bbe61

  	logger.info("Evaluation")
  	# TODO: metrics should be computed at evaluation time, not during training
  	# compute metrics

• Training of Morphometrics classifiers:
  

  morphoclass/src/morphoclass/console/cmd_morphometrics.py

  Lines 198 to 200 in 35bbe61

  	logger.info("Evaluation")
  	# TODO: metrics should be computed at evaluation time, not during training
  	# compute metrics

Actions

• Make sure that nowhere else in the code (e.g. during evaluation) we are assuming that the checkpoint.chk produced during training contains metrics scores.
• Move the computation of metrics scores from training stage to evaluation stages.

See also

#45 (comment)