Slice Indexing within Chunk Files

[olls]

One limitation of the chunk files are that each line of the file has a variable length, because the slice index can have any number of digits. If we make the slice indexes within the save files relative to the chunk position, then we can pad the slice positions to a constant width. This would also remove the need for the SLICE_SEP.

[olls]

Or we could get rid of the position entirely and just use the line number

[olls]

93c20acce5a87feaa5477b642f81db7ed499d282