Fix sudo help and summaries
    
    1) Add sudorule docstring headline
    
    2) Fix naming inconsistency in Sudo plugins help and summaries,
       especially capitalization of Sudo objects - Sudo Rule, Sudo
       Command and Sudo Command Group
    
    3) Add missing summaries for sudorule-add-option and
       sudorule-remove-option. To keep backward compatibility with
       older clients, just print the missing summary with
       output_for_cli(), don't expand Output.
    
    https://fedorahosted.org/freeipa/ticket/1595
    https://fedorahosted.org/freeipa/ticket/1596