part of fixing assemble
simplify bash argument parsing
allow users to pass CSON via --locals cli argument

valid examples:

borg assimilate aws-or-prod-mybox01.mydomain.tld \
  --locals ssh:port:1234
borg assimilate aws-or-prod-mybox01.mydomain.tld \
  --locals '{ "ssh": { "port": 22202 } }'
borg assimilate aws-or-prod-mybox01.mydomain.tld \
  --locals '{ ssh: { port: 22202 } }'