Updates for a more sophisticated development experience.

Support for external files for installation. The NSight systems debian binary cannot be installed via the command line. An external .deb file is therefore used.
Also, Git Large File System (LFS) is used to prevent the .git directory from bloating.
The build guidelines have also changed in order to make the meaning clearer (I think). CCA is no longer mandatory and the .env file is guarded by a separate recipe.
Python package installation is now fully parallel with apt package installation.
Finally figured out how to get separate volume paths for different hosts. Using docker-compose.override.yaml was decided to be the best approach.
Documentation still needs work.