Remove getLoadedData API from ExoPlayer components.

This API wasn't particularly nice. Best to remove it whilst
hopefully no-one is using it. Leaving the ReadHead abstraction
in place, since it might well prove useful in the future.
Fix SmoothStreaming where audio FourCC is missing.
Remove unused import. Tweak documentation.
Resolve reference Uris correctly.

Ignore the path of the base Uri if the reference starts with "/".
Spec - http://tools.ietf.org/html/rfc3986#section-5.2.2
Ensure that we try and call release on a renderer

Do this even if stop/disable fails.
SmoothStreaming - Parse last chunk duration.
Add WebVTT parser.
Auto-infer character encoding.
Enhance Loader API.