documentation

Pull request #978: Feature/ZBXNEXT-8326 7.0 D

Merge in WEB/documentation from feature/ZBXNEXT-8326-7.0-D to release/7.0

* commit '790f4aa2aefd48ebf3915a216da2ae07f84edca9':
  png updated
  Dianas suggested change applied
  M.Prih. suggested edits applied, v7.0
  link added to whatsnew700
  picture changed
  periods added
  sys-info table update for vers 7.0