Reimplement ExtractImagePatches' create_kernel_tensor with Range & Scatter

[tzerrell]

I believe that we could avoid compute_shape in ExtractImagePatches' create_kernel_tensor function by using a Range op that takes a TensorDim parameter along with Scatter. However, such a Range op has not yet been implemented. Moreover, I'm not quite sure if switching to TensorDim there would get in the way of optimizations noticing that everything involved was a constant.

Investigate whether the above approach would work as desired, and if so implement it.

See also #96