MA-104 Studio backend for video_upload

https://openedx.atlassian.net/browse/MA-104
Advanced Setting for "Video Upload Pipeline".
Feature Flag for "ENABLE_VIDEO_UPLOAD_PIPELINE".
Use AssetMetaData store to persist video upload information.

@andy-armstrong @gwprice I have created this new PR to reflect only the initial backend studio support of our feature.  Please review again.  
This is the common AWS key used throughout the platform.  We want to use the same set of keys for the video pipeline feature.