Blender Git Loki

Write StampData metadata to video files

This is currently only supported by FFmpeg (so not frameserver, AVI RAW,
or AVI JPEG), and only seems to work when using Matroska or Ogg Theora
containers.

Only metadata that doesn't change from frame to frame is written to
video files. This distinction is visible in the UI by looking at the
stamp checkbox tooltips (they either mention "image" or "image/video").

Part of: https://developer.blender.org/D2273

Reviewed by: @campbellbarton