Add also FLAC/MP3/WAV support for music and replace hardcoded "keeperNN.ogg" requirement with now automatic music file detection

[AleWin32]

This PR adds support for FLAC files (lossless compression) in addition to OGG (lossy compression), which is currently the only format KeeperFX supports.

This PR does not remove OGG support, it now adds FLAC, WAV and MP3 as well.

It also changes how tracks are located: the audio tracks are now read regardless of their filename (no fixed keeperNN.ogg pattern is expected), avoiding trouble for KeeperFX players who want to extract the audio themselves.

The music folder is now listed and sorted by name in ascending order, so the tracks are always detected automatically.

Since tracks are usually extracted numbered by track, all of these naming patterns work:

Untitled 02.ogg/flac
Untitled 03.ogg/flac
...

Track 02.ogg/flac
Track 03.ogg/flac
...

keeper02.ogg/flac
keeper03.ogg/flac
...

It even works when the filenames don't contain the audio track number at all, or use numbering starting from 0 or 1, thanks to the ascending sort:

music00.ogg/flac   -> track 2 (the first file in the list is always treated as track 2)
music01.ogg/flac   -> track 3
...

audiocd01.ogg/flac -> track 2 (the first file in the list is always treated as track 2)
audiocd02.ogg/flac -> track 3
...

The preference is to preserve 100% of the original audio quality today while using as little storage space as possible.
Therefore, this is the preferred order in which the formats are attempted:

• FLAC (lossless quality, compression): Audio quality is 100% identical to the original while taking up less storage space.
• WAV (lossless quality, uncompressed): Audio quality is 100% identical to the original, but it requires more storage space.
• OGG (lossy compression, compressed): Audio quality is not 100% identical to the original, but it takes up little storage space and offers better quality than MP3 at the same bitrate, thanks to its more advanced psychoacoustic model.
• MP3 (lossy compression, compressed): Audio quality is not 100% identical to the original, but it takes up little storage space.