* Chunks replay skips chunks with unknown encodings
We've changed the logic of loadMmappedChunks to skip chunks that have
unknown encodings. To do so we've modified IterateAllChunks to accept an
extra encoding argument in the callback function.
Also added unit tests in the head and chunk disk mapper.
* Also add an unit test for the old chunk diskmapper
* s/createUnsupportedChunk/writeUnsupportedChunk/g