* Use string keys. I am still convinced we need BValue.
* Use boolean instead of status_t in return, this is
much more handy in pratical use given that there's no
really a status to check.
* Those classes are not ready for public consumption. Ideally,
I'd add a well designed BCodecRoster wrapping them. This is part
of the general cleanup I am doing to get the code in a good state
before going to finalize the design.
* I don't plan to reintroduce BMediaFile in the media2 API, and
I'd like to remove any (explicit) usage of entry_refs and things
like that.
* I plan to introduce BMetaData and BMediaFormat which is going
to be different than what we do now.
* We need to explicitly use the mime type when it's available and
it is another design consideration when CodecRoster will be introduced.
