Don't mirror natives in FFmpeg: make it own them
Fix makeBETag using only 2/4 chars
Sanitize makeBETag string argument
Wrap log levels
Lots of work on media API

* Switch to direct method mapping - much faster
    * LibAV- methods statically importable
* Refactor AVPixelFormat & AVSampleFormat to better-named enums
* Implement changing of FFmpeg log level
* Implement abstract media decoding API
* Implement a Swing media player panel

Refs #103 @15h