[saliencymap_evaluator] Reimplements interpretability evaluator to simplify code, be less dependent on opencv, improve documentation, and improve type hinting

[engine,scripts] Simplify saliencymap generator; Add more type hinting; Make it TB-agnostic; Closes #49

Merge branch 'add-datamodule' of gitlab.idiap.ch:biosignal/software/ptbench into add-datamodule-gradcam

This reverts commit 20dfcdb4.

[test/test_cli] updated unit tests for training, prediction and evaluation cli scripts. Removed radiological signs (rs) related tests