refactor project to use "-label.json" as a marker

[CXwudi]

• instead of scanning -songInfo.json, we should use a dedicated JSON file with all other necessary info for the next module to proceed. The JSON info also includes any filenames associated with the song (including songInfo.json file)
• this can also fix the issue: to implement an advanced audio extractor choosing strategy, we need information from the previous module.
• don't write too many util functions for labels, instead, each module has its own helpers (reason: for better extendibility)
• also don't be confused that this label JSON is used to record necessary info and parameters that the next module needs
  • it is not the aggregated parameter object in use aggregated parameter object #8

[CXwudi]

At this stage, we are pretty sure we are using "-label" JSON all the time