v2.4.0

Software changes:

• Re-organise the code to support standard setup.py
• Portage to python3
• Fix handling of job exclusive field in dashboard
• Introduce RPM el8 packaging

Debian specific changes:

• Introduce slurm-web-common package to install slurm-web Python module files common to all slurm-web python packages. making slurm-web binary package a meta-package to install all Slurm-web components.
• Bump d/compat to 9