Improve multimedia support

It's not really clear how and which media types are supported by kompakkt. Also it's not clear what kind of features (like annotating) are working for specific media. We need to do a good documentation and also decide if we want to keep audio, video, images and sound in addition to 3D.

Review the repository to inventory which audio, video, image, sound, and 3D media types are currently supported and which annotation features work for each. Document the findings clearly and record the decision about which media types Kompakkt should continue supporting.

Written by the indexing model from the issue text.