Use new project build tool poetry

[mgkwill]

Objective of issue: Remove pybuilder and add build tool poetry

Lava version:

• 0.3.0

I'm submitting a ...

• bug report
• feature request
• documentation request

Current behavior:

• pybuilder has some bugs and does not currently support editable install on Windows and running unit tests on any OS due to some virtual environment issues that are hard to pin down. The community that runs pybuilder is small and they seem less open to fix bugs when reported (I've seen bugs that reference above issue that were turned down). The result is a decision to remove pybuilder as the build agent and replace it with poetry, flakeheaven and pytest and use a central pyproject.toml as the configuration source for builds and QA tools.

Expected behavior:

• Poetry, flakeheaven and pytest are in use, configured with a central pyproject.toml for builds and QA tools. Docs are updated to reflect new tools.