* Ideally we should support this feature by default to allow
future improvements to the plugins management.
* Fixes the major memory corruption that lead to various
crashes on exit in MediaPlayer.
* There's no need to force the streamer plugin to use a
BMediaIO. This class is supplied to accomodate more smart uses,
but in certain cases it makes just things more complex. If a
plugin doesn't need to have an internal caching method, then it
will be simpler to implement a block-consuming BDataIO and let
the internal BMediaIOWrapper to deal with caching.
