This PR groups misc cleanup and changes from https://github.com/ooni/probe-cli/pull/331.
* CLI/linux/build: add documentation
* debian/.gitignore: ignore generated files
* debian/TODO: unnecessary at this point
* debian/ooniprobe-cli.service: remove commented out lines
* debian/rules: remove unnecessary actions
* make: reindent and fix spelling
* smoketest.sh: don't run in verbose mode
Part of https://github.com/ooni/probe/issues/1466
