- cleanup package summaries/descriptions
    
    In particular:
    
    * respective lines should be no longer than 80 characters
      https://fedoraproject.org/wiki/Packaging:Guidelines#Summary_and_description
    
    * there's no point to restate package names in the descriptions
    
    * some minor cleanups (trailing whitespaces, missing dots in
      descriptions [for uniformness], hefty wordings)
    
    Signed-off-by: Jan Pokorný <jpokorny@redhat.com>