One RIKOLTI_DATA to rule them all

[amywieliczka]

This PR:

• Deprecates VERNACULAR_DATA, MAPPED_DATA, WITH_CONTENT_URLS_DATA, and MERGED_DATA environment variables in favor of RIKOLTI_DATA.
• Updates CONTENT_ROOT to RIKOLTI_CONTENT
• Adds a python -m utils.s3copy utility that takes an s3 URI & a local filesystem path to pull down to the local filesystem some arbitrary s3 folder, maintaining relative paths.

[barbarahui]

Looks good! Yeah, I didn't ever make use of the finer distinction that used to exist between the various data locations env vars.

And in the darkness bind them!