Pack the internal modules of Cortex into a Python package

[RobertLucian]

Description

Create a Python package containing all internal modules belonging to Cortex instead of importing them using absolute/relative paths.

Motivation

It can avoid collisions with modules added under the root directory of a Cortex project. It also helps in keeping the development environment cleaner (and more compact). Reduces the coupling.

Additional context

Use the standard setuptools package to create the Python package.
When installing the Cortex Python package into each of the images' environments, use pip install -e . to allow live editing of the package.