Use poetry for dependencies management

[chiragjn]

See: #190

Starting this is an intial draft to move to poetry

TODO:

• [ ] Test Dockerfile changes
• [ ] Make cognita a publishable package (#191) - We do not want our users to worry about poetry
  • [ ] Refactor to put source code in a cognita module - Changing imports
  • [ ] Add cli to invoke serve and index - Update entrypoints in pyproject.toml
  • [ ] Update Dockerfile
  • [ ] Remove requirements.txt
• [ ] Add a workflow to publish package
• [ ] Update Docs

Later:

• [ ] Add a workflow to publish docker images
• [ ] Setup pytest and add a workflow