Do not carve out chunks when the chunk covers the whole file

[martonilles]

If the chunk equals the whole file we can omit carving out that (basically copying) the whole file as any extractor can work on the original file instead. As we would be also cleaning up the carves after extraction there is no benefit of doing so. This could save some disk IO and also some disk space during extraction.

Further this would also help with handlers without extractor as they wont extract chunk if a handler matches the whole file.

Similar discussion from #82 #23

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Questions:

• how the directory structure should look like in this case? Should we skip 1 directory level in this case or we want the directory levels to be the same, regardless of this optimization?
  • we can keep the directory structure to be consistent and it would also show the offsets
  • on the other hand it is an empty directory with one subdir only and the offset is less interesting as it is the whole file
  • DECISION: skip the directory for these cases