Preserve whitespace

[russellpierce]

This PR stacks on #8 and #10 and is an important fix for #8 in so far as whitespace is important in memory retrieval. The problem: the initial CLI used rich formatting of results as a default. This introduced newlines in JSON payloads that can interfere with a memory key being piped and directly used as a python program. This PR makes --rich formatting opt-in rather than the default so that whitespace is easily preserved / we don't introduce unexpected newlines.

E.g. I have instructions to

# Generic pattern:
CLI="path/to/ensue-cli.py"

$CLI get_memory --key-names '["code/some/script-key"]' | \
  python3 -c "import sys, json; print(json.loads(sys.stdin.read())['results'][0]['value'])" > /tmp/script.ext && \
  <runtime> /tmp/script.ext [ARGS]