Add the desc of --self-manage option

and fix help description algorithm

Related to #311

autoload/options/__help__

@@ -74,6 +74,7 @@ fi
                 printf "\n$obj:\n"
                 ;;
             *)
+                desc="(None)"
                 [[ -n $opts[$obj] ]] && desc="$opts[$obj]"
                 [[ -n $cmds[$obj] ]] && desc="$cmds[$obj]"
                 printf "  %-${max}s    %s\n" \

autoload/options/__self-manage__

@@ -1,4 +1,6 @@
 #!/usr/bin/env zsh
+# Description:
+#   Self management of zplug
 
 if ! __zplug::base::base::zpluged "zplug/zplug"; then
     __zplug::io::print::f \