Land rapid7#8141, fix execute and kill cmd usage/help

Author: bwatters-r7

lib/rex/parser/arguments.rb

@@ -76,6 +76,7 @@ def usage
           txt << "    #{fmtspec.ljust(longest.length)}#{opt}#{val[1]}"
         end
 
+        txt << ""
         txt.join("\n")
       end
 

lib/rex/post/meterpreter/ui/console/command_dispatcher/stdapi/sys.rb

@@ -371,6 +371,15 @@ def cmd_kill(*args)
     return true
   end
 
+  #
+  # help for the kill command
+  #
+  def cmd_kill_help
+    print_line("Usage: kill [pid1 [pid2 [pid3 ...]]] [-s]")
+    print_line("Terminate one or more processes.")
+    print_line("     -s        Kills the pid associated with the current session.")
+  end
+
   #
   # Kills one or more processes by name.
   #