BufferedData slices are still broken

[artemananiev]

The fix for #83 is incomplete. I use BufferedData.readVarInt() in MerkleDb, it was touched in that fix, but some pieces are still missing.

In particular, to read bytes BufferedData now takes wrapped buffer offset into consideration:

        int tempPos = buffer.position() + buffer.arrayOffset();

However, when it needs to forward buffer position later, the offset is ignored:

            buffer.position(tempPos);

Instead, it should be

            buffer.position(tempPos - buffer.arrayOffset());

There may be more places broken like this.