Remove `docbook' and `linuxdoc' backends from `help' functionality.
    Only `texinfo' backend remains. 
    
        - The `texinfo' backend seems to be fairly complete by now and is
          the one used as reference inside `centos-art.sh' script when
          errors occurs.
    
        - The initial intention of `help' functionality was to automate
          the process of creating/maintainig documentation related to each
          repository directory structure in different languages. The
          `help' functionality creates one documentation structure for
          each language you want to support documentation. Inside each
          language-specific documentation structure there is one
          documentation entry for each directory inside the repository.
          The `help' functionality is responsable of creating, reading,
          editing, copying, deleting, renaming those documentation entries
          in each specific documenation structure.
    
        - I'll use the `help' functionality only to document the manual:
          The CentOS Artwork Repository References. All other
          documentation manuals will be organized personally. Do not
          impose fixed structures on new documents.