CLI, debian, make: misc cleanup and changes (#336)

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

debian/rules

@@ -6,12 +6,10 @@ export DH_VERBOSE=1
 	dh $@
 
 override_dh_auto_clean:
-	rm -f debian/ooniprobe.1
 	dh_auto_clean
 
 override_dh_auto_build:
 	# The ooniprobe binary is provided
-	./CLI/linux/amd64/ooniprobe --help-man > debian/ooniprobe.1
 
 override_dh_dwz:
 	true