Deeppixbis extractor

Added the extractor for DeepPixBiS, since it was not present here, but only in the following paper package: bob.paper.deep_pix_bis_pad.icb2019

I guess it's better to have it here as well !

bob/learn/pytorch/extractor/image/__init__.py

@@ -5,6 +5,7 @@ from .MCCNN import MCCNNExtractor
 from .MCCNNv2 import MCCNNv2Extractor
 from .FASNet import FASNetExtractor
 from .MCDeepPixBiS import MCDeepPixBiSExtractor
+from .DeepPixBiS import DeepPixBiSExtractor
 
 __all__ = [_ for _ in dir() if not _.startswith('_')]