12.b Local-algorithm ported.

We need a mean to abstract away the way we iterate locally around a pixel.

Task 1: Local algorithm canvas.

• Handle constant border and user-custom border extension
• Mind that the border management might be dynamic
• Border-management is well-documented
• Local algorithm canvas is well-documented
• Local-accumulation canvas + documentation

Task 2: SE-based morphological operators are ported using the new impl.

• Dilate/erode + doc + bench (!69 (merged))
• Opening/closing + doc + bench (!70 (merged))
• Hit-or-miss + doc + bench (!70 (merged))
• Rank / median filter + doc + bench (!73 (merged))
• Morphological gradients + doc + bench (!78 (merged))

Task 3: Nbh-based algorithm are ported using new impl.

• labeling/blobs + doc + bench (!90 (merged))
• labeling/local_extrema + doc + bench (!75 (merged))
• labeling/rag + doc + bench (!90 (merged))
• transform/chamfer_distance_transform + doc + bench (!77 (merged))