Fix man and commandline docs

- missing help option in `docs/reference/commandline/*.md` (some files
  have it, the other I fixed didn't)
- missing `[OPTIONS]` in Usage description
- missing options
- formatting
- start/stop idempotence

Signed-off-by: Antonio Murdaca <amurdaca@redhat.com>

docs/reference/commandline/stop.md

@@ -13,10 +13,11 @@ weight=1
 
     Usage: docker stop [OPTIONS] CONTAINER [CONTAINER...]
 
-    Stop a running container by sending SIGTERM and then SIGKILL after a
+    Stop a container by sending SIGTERM and then SIGKILL after a
     grace period
 
+      --help=false       Print usage
       -t, --time=10      Seconds to wait for stop before killing it
 
 The main process inside the container will receive `SIGTERM`, and after a grace
-period, `SIGKILL`.
+period, `SIGKILL`.