Simplify the MultiNetPatchExtractor and MLPAlgorithm

Hey @heusch ,

As you pointed out these two classes are controlled by configs:

https://gitlab.idiap.ch/bob/bob.ip.pytorch_extractor/blob/master/bob/ip/pytorch_extractor/MultiNetPatchExtractor.py

https://gitlab.idiap.ch/bob/bob.ip.pytorch_extractor/blob/master/bob/ip/pytorch_extractor/MLPAlgorithm.py

Completely agree with you, this is not convenient resulting to have "configs in the configs".

Will refactor that tomorrow, removing the need for controlling configs in above files. Please let me know if you have any comments on that. Thanks!