Implement non-axis windows and chunks iterators

Start by reviewing the existing ExactChunks, ExactChunksMut, and Windows implementations and their NdProducer implementations. Clarify whether the remaining work is RaggedChunks/Chunks, non-axis windows, or full-window behavior, then define the valid and edge cases described in the issue. Done means the requested n-dimensional iterators and corresponding NdProducer implementations are covered.

Already implemented features and todos:

• ExactChunks and ExactChunksMut aswell as their NdProducer impl
• RaggedChunks or simply Chunks aswell as their NdProducer impl
• Windows
• NdProducer impl for Windows

Implement n-dimensional windows and chunks iterators.

Windows-iterators are especially useful for convolutional neural networks while chunk iterations may prove useful for paralell algorithms.

N-Dimensionality for both iterators use N-dimensionally shaped items.

For example for a 1-dimensional Array the windows and chunks items are also 1-dimensional.
For a 2-dimensional Array the windows and chunks items are 2-dimensional, and so on.

For windows iterator it could be useful to support two different kinds of windows iterators.
One for "valid" windows only that iterate only over windows within a valid region.
For example in a valid-windows iterator over a 10x10 shaped 2d-array and window sizes of 4x4 the iterator would iterate totally over (10-4+1)x(10-4+1) items of size 4x4.
A full-windows iterator would also iterate over the windows with invalid elements (on the edges of the array) and would simulate missing elements with zero elements.

Semi-nice visualization of n-dimensional chunks and windows iterators.

A similar approach could be used for n-dimensional chunks that iterate beyond the array sizes and replace missing/invalid array elements with zero elements.