Add support for youtube playlists

[qzdl]

What it says on the tin

• Investigation required for the youtube API to provide a similar configuration setup to spotify
• CLI amendments to explicitly state platform
• Refactor of sample_finder to generalise parsing
• base class for common APIs
  • new module with spotify mappings, ported from sample_finder :: base class
  • new module with youtube mappings :: base class

[qzdl]

Documentation
Playlist Creation Console
Playlist API reference

[qzdl]

PR has been updated with SRC structure changes, though coming back to it makes me hate the CLI api. Will rework such that spotify is the default for input/output, but all the permutations can be explored