Add version and flags to standard_features

[podborski]

It would be really helpful if we store box versions and flags for each FullBox. This would allow us to search for a box of a specific version of flags. Here is an example on how our current json files could be extended:

      "versions": [1, 2, 3],
      "flags": [
      {
        "name": "track_enabled",
        "value": "0x01"
      }, ... ],
      "syntax": "..."

There is some work Cyril did for mp4box.js which can be used to update this fields