Support other segmenters than ffmpeg

[MichalCz]

Create modularized reader that would allow using any module to read the chunk list in place of current ffmpeg-specific csv reader.

The segmenters could be:

• the current csv format
• m3u8 reader - if a progressively written m3u8 file would be sent to webdav then that could be our chunk list reader
• fs reader - some settings like a glob pattern that would identify which files are chunks and Streamed access to chunks. #1 would make us not need to have a chunk list at all.