Make sourcing scripts path relative to script, not current working directory

[dacabdi]

The entry point setup script cannot source the other scripts if the current working directory is not the root of the repository. It would be more robust to make all sourcing relative to the root of the repository.

[g00nix]

I think this is covered by these two PRs:

• https://github.com/pia-foss/manual-connections/pull/94
• https://github.com/pia-foss/manual-connections/pull/90

Please confirm if these PRs solve your issue, so that we can proceed to clean them up and merge them.

[dacabdi]

Yes @g00nix, I think that works.