Various updates to code dependencies and packaging

[piconti]

This merge request perfoms various updates, in particular fixing issues related to depreciated code and dependencies:

• Shift to pyproject.toml for packaging
• Update to requirements.txt to match dependencies updates
• Removing the use of the depreciated boto package in favor of its counterparts using boto3
  • Functions that previously used boto have been kept, along with depreciation warnings.
• Removing the use of pkg_resource in favor of importlib.resources
• Updating and fixing some tests ( to fix #75 )
  • Futher changes to the tests and removal of some depreciated funtions will still be necessary in the future.

The package's version is now consequently 0.13.0. The Pipy distribution was updated in consequence.