[*] Implement automatic second-annotator evaluation

bob/ip/binseg/configs/datasets/chasedb1/first_annotator.py

bob/ip/binseg/configs/datasets/chasedb1/second_annotator.py

bob/ip/binseg/configs/datasets/drive/default.py

bob/ip/binseg/configs/datasets/stare/ah.py

bob/ip/binseg/configs/datasets/stare/vk.py

bob/ip/binseg/engine/evaluator.py

bob/ip/binseg/engine/predictor.py

bob/ip/binseg/script/evaluate.py

bob/ip/binseg/script/experiment.py

bob/ip/binseg/script/predict.py

bob/ip/binseg/test/test_cli.py