Improve initial setup for local dev

[mihow]

• Create a default user on initial startup (see README)
• New management command create_demo_project to create additional test projects with synthetic data at any time (or on top of an existing DB)
• Remove unused services from the docker compose stack to help speed up dev on local machines
• Show output from yarn proxy server while building & serving pages
• Fixes issue where user cannot be logged into Django admin and React UI at the same time! Closes Forbidden error, Jobs fail to start #369
• Other fixes to ease local development when starting fresh

[netlify]

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