documentation

Pull request #4385: ZBXNEXT-1150 updated JSON examples, updated parameter descriptions, added a what's new entry, API changes entries, updated relevant descriptions about maintenance and event suppression.

Merge in WEB/documentation from feature/ZBXNEXT-1150-7.5-D to release/8.0

* commit 'a508ddd4d0a3e3fca28aa12235f46082b8882c66':
  ZBXNEXT-1150 fixed sentences to match the ones in the table
  ZBXNEXT-1150 removed redundant sentence.
  ZBXNEXT-1150 added icons to sentences for clarity.
  ZBXNEXT-1150 added missing period.
  ZBXNEXT-1150 fixed images paths.
  ZBXNEXT-1150 added icons, their description, fixed redundant wording and missing space.
  ZBXNEXT-1150 updated screenshots, a what's new entry, added info about icon color.
  ZBXNEXT-1150 corrected a link. moved parts of desctiption, substituted phrases. other minor fixes.
  ZBXNEXT-1150 updated JSON examples, updated parameter descriptions, added a what's new entry, API changes entries, updated relevant descriptions about maintenance and event suppression.