split up lasagne.layers.base into submodules
import the required layer classes in the doctests themselves
Looks like the explicit import of cuda_convnet and corrmm isn't even necessary, the submodules are there already.
add more documentation for the Layer base classes
amend Layer class docstring following @f0k's suggestion
Merge pull request #81 from benanne/split-layers

split up lasagne.layers.base into submodules