[architectures] added DCGAN in __init__.py

bob/learn/pytorch/architectures/__init__.py

 from .CNN8 import CNN8
 from .CASIANet import CASIANet
 
+from .DCGAN import DCGAN_generator
+from .DCGAN import DCGAN_discriminator
+
 # gets sphinx autodoc done right - don't remove it
 __all__ = [_ for _ in dir() if not _.startswith('_')]