self contained campaign directories

[bd4]

It would be useful if Cheetah campaigns could be run without having a specific spack package or python path set to find the workflow script and it's dependencies. One option would be to run python3 setup.py install with a --root somewhere in the campaign dir. Another option would be for the campaign to have a configure script that sets PYTHONPATH to the cheetah install that was used. The advantage of the full install is that it allows passing the campaign dir off to other users, or saving it for later use with no external dependencies. As Cheetah evolves, there may be releases that break backward compatibility so an old campaign may stop working.

This came up with WDMApp where Cheetah is used inside effis, and installed via spack as a dependency. We provide a sample setup{MACHINE}.sh, which must be edited by hand to at least include the users spack root, so the appropriate spack loads can be done and the workflow can run. The instructions also require manually changing exe paths in the the effis run YAML, so this isn't the only manual path setting step. Ideally we can work towards removing all these manual per-install customization steps.