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 (Feature Request: Publish Cognita as a package to pypi #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

[chiragjn]

This does not exist relative to this file
We want to move pyproject.toml to root

[chiragjn]

I'll re-open this later, we already have conflicts with recent changes