Magic Hash - and no L0 Index

Move to using the DJ Bernstein Magic Hash consistently, and trying to
make sure we only hash once for each operation (as the hash is more
expensive than phash2).

The improved lookup time for missing keys should allow for the L0 index
to be removed, and hence speed up the completion time for push_mem
operations.

It is expected there will be a second stage of creating a tinybloom as
part of the SFT creation process, and then adding that tinybloom to the
manifest.  This will then reduce the message passing required for a GET
not in the cache or higher levels

src/leveled_log.erl

@@ -165,7 +165,7 @@
     {"I0013",
         {info, "File ~s to be removed from manifest"}},
     {"I0014",
-        {info, "On startup oading from filename ~s from SQN ~w"}},
+        {info, "On startup loading from filename ~s from SQN ~w"}},
     {"I0015",
         {info, "Opening manifest file at ~s with SQN ~w"}},
     {"I0016",