Document how to move bucket off Terra

[brendanreardon]

It would be worthwhile to document how to move a bucket away from Terra. Items involve

• Creating a non-Terra bucket
• Sharing the bucket with all relevant proxy-accounts (pet accounts) from Terra
• Updating paths in data model and workspace annotations
  -- Could write a script for this but it may break for arrays of arrays of arrays.
  -- A method could be launched that update strings of arrays into proper arrays.

[brendanreardon]

I updated the documentation for archiving a workspace but have not written documentation on bucket sharing and such
https://github.com/vanallenlab/terra-helper/blob/master/use-cases/archiving-a-workspace.md