Changes and fixes for new API release

[pbricout]

Trying to list the changes and fixes we want to do for the next API release

Public API changes:

• remove support of string (which is implicetely encoded as UTF8) for the data member in private frame
• align frame types between read and write (make read and write isomorphic)
• separate buffer and file operations
• noRaw option should also apply for tags Chapters and TOCs (should be recursive)
• Promises should only work with files, there is no point having an asynchronous API for Buffers since there are synchronous operations
• align all tag aliases names (and terminology) with the ID3 documentation (some tag aliases use a different terminology)
• enable all multiple frames
  • unsynchronised lyrics (USLT)
  • attached picture (APIC)
  • others?
• support image file links in APIC frame
• remove the update function, there are edge-cases especially with multiple frames we can't deal with the function correctly, read and write should enough and more flexible
• read will return an object with frames (known frames), unknownFrames (with a buffer for each frame) and undecodableFrames, write will consume the same object (unknownFrames and undecodableFrames could be merged in a single undecodableFrames where the reason for un-decodable could be either unknown or an error)
  • define a format for unknownFrames and undecodableFrames
  • undecodableFrames should have extra information which indicate the failure
  • should the read function provide extra frame information from the frame header? (frame id, size, etc.) or
  • should we provide a utility function to extract information from a frame header (I would say yes)
• have some thoughts of how to deal with identifiers and aliases (remove aliases???)
  • write will only accepts identifiers and we provide a converter to convert from aliases to identifiers
  • read will only return identifiers and we provide a converter to convert from identifiers to aliases
  • this is flexible, robust, composable and simpler
• try to make zlib and fs dependencies run-time and injectable dependencies to improve portability
• maybe provide a write option to choose the string encoding scheme

Possible future public API improvements:

• provide the ability to write custom frame handlers

Internal changes:

• add an option to FrameBuilder to emit an encoding byte
• name "at least" size parameter in FrameBuilder and FrameReader as very often this is a static value
• rename FRAME_OPTIONS to FRAME_PROPERTIES I think this is more appropriate

Related issues:

• issue Adjust all callbacks to (err, val) #85
• issue [feature] Add support for React Native #113