Implement byChunk - a range that instantiates a pipeline and reads from it by chunk.

[epi]

Call byChunk() without arguments if you don't care about the size of a chunk and you're able to process chunks of any size.
Call byChunk(size_t chunkSize) if you require chunks of specific size.
Call byChunk(T)(T[] buf) if you require chunks of specific size and you want to manage the buffer where they'll be stored.

byChunk should implement input range interface as well as opApply() iteration.
byChunk should be optimized according to the pipeline's last stage source method and required chunk size and buffer ownership.