Mobile/studio video upload

https://openedx.atlassian.net/browse/MA-104
@andy-armstrong please review.  This is the initial PR for the video upload pipeline work.
@gwprice please review.
@doctoryes FYI - first usage of the AssetMetaData store.

Is ```&gt;``` a universally agreed separator in all languages? Does it work in right-to-left? FYI @cptvitamin