FFMPEG integration

[voylin]

FFMPEG is needed for nearly all complicated functionalities inside of GoZen and will be responsible for following items:

• [ ] Thumbnails;
• [x] Loading/Importing videos;
• [x] Displaying frames;
• [x] Rendering;

This would provide us with codec support for nearly all video files.

The way to integrate ffmpeg is being tried by using GDExtensions and C#, we will use whatever works first.

[voylin]

The whole ffmpeg related stuff has been taking longer then I thought it would, it's slowly coming along. This part also moved out to a GDExtension which is being build in a separate repo.

[voylin]

We got basic ffmpeg functionalities, thumbnails will be for later however.