Ability to extract annotation/frames from clips rather than video

[eacharya]

• In addition to video id, we should also export clip path, clip id and clip frame number
• Each annotation export should also include 4 "AVOID" class to account for embedded frame counter (introduced by #10) at the corner of each frame

This is a follow up to issue #11 and not immediately needed since we are extracting frames from original video rather than clips.