Cloud: Write RFC that clarifies cloud information architecture and implementation

Created by: ryanslade

The RFC should clarify the informations architecture and implementation required to allow users to add and search their own or organisation code on sourcegraph.com

Items to consider:

• Repo ownership
• Repo permissions
• Repo curation
• Organisation membership / hierarchy. An org on SG could be associated with multiple external orgs

All of the above should take into account both public and private code.