New interface for scan

Gpuconv

fixed bug in min_informative_str

Fix syntax error, remove unused import.

I used to call as_tensor_variable which is not ok for sparse or
random generators

node.

sequences are not a list of dictionary anymore, but a list of tensors,
the original tensors.

Now scan requires the user to say the number of steps. In case of outputs
that do not feed anything in, if the user does not provide any information
then it is assumed that you want all intermediate steps.

fix crash introduced during pep8 fix.

Gpu specify shape

Sparse

place. Also add the infer_shape method to Remove0

Minor stuff