server: Rename status "status" map to "instances"
server: Rename "token" to "instance"

Use "token" only to mean the authorization string that identifies an
instance.
server: Fix typo
server: Split token into instance ID and auth code
server: Add instance ID to status output
server: Add decorator for requiring HTTP auth
server: Use /instance endpoint for status
server: Add HTTP endpoint for destroying an instance
Fix pylint warnings