Update texinfo templates.
    
        - Don't include index as default configuration. It complicates
          localizing repository documentation manual in texinfo format.
          
        - The manual index needs to be added by hand, it is out of
          repository documentation structure, it is not a documentation
          entry so treat it as such complicates everything. In that sake,
          don't include index as default configuration, when new
          language-specific repository documentation manual be created.