Preserve extra data when encoding/decoding Engine blobs

Change encoded blob representation to std::byte rather than char.
Preserve extra binary data when decoding/encoding blobs. This can help with compatibility of future versions, as mentioned in #99.
Fix some string-rendering typos.
Update the track data format to the new "v2" arrangement, which is backwards-incompatible with v1.
Always set the cue point to be "adjusted" in the high-level API, as otherwise hardware players will default to their own derived one.

xsco / libdjinterop