pep8
Don't enable the GPU version of conv3d ops, as they aren't tested and bugged and VERY slow!
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pep8
Give info on how to enable fft conv on only 1 Theano fct.
Add new link to python tutorial.
Fix formating issue with as_op doc and add exercices solutions.
Remove detail about as_op and make it clear this isn't recommand.
Make CudaNdarray_NewDims always set the python exception.
Don't hide the real error during error handling code.
fix typo.
typo fix following code review.
Merge pull request #2043 from nouiz/mixed

Mixed stuff: pep8, comments, doc, don't enable GpuConv*3D op by default at that module import.