Feature Request: default/auto parameters for training about calamari

[ChWick]

• As of bb79ecf: early stopping frequencies may be relative to epochs (if <= 1), default = 0.5.
• early stopping number of best models set to 5
• max iterations is unchanged, usually this parameter should never be required, because training with a validation set is recommended. Alternatively, the training can always be stopped manually.
• By default the checkpoint frequency uses the early stopping frequency if not explicitly stated.