Rewrite the whole thing with Ruby / Python

[5long]

For now p3wm relies on bash's set -u feature to fail fast. This is fine for a in-house sysadmin's script / personal project. But the error messages aren't very user-friendly for end-users. To print a user-friendly error message, set -u just isn't good enough and I can't check empty variables with [[ ... ]] anymore since the -u takes higher precedence.

Maybe it's time to rewrite in a more maintainable programming language rather than taking the bash shortcut.

[5long]

It works fine for now. Don't bother to do a full rewrite.

[5long]

Running with P3WM_DEBUG=1 prints too much information. I think I need a logging library to handle debug logging. Switching to Ruby / Python could probably help with debugging.