ffmpegGUI: update to v1.2

* Added job manager
* Added cropping preview and moved to own tab
* Save/Restore window position
* New "ffmpegGUI" menu for Quit, About, Help, FFmpeg docs
* Added help documentation
* Changed PCM codec option to pcm_s16be (which is expected by the MPG container)
* Removed translations below 80% finished (ca, es-419, id, pt_BR, ru)