documentation

Pull request #346: [ZBXNEXT-7852] Updated documentation for incremental active check refresh.

Merge in WEB/documentation from feature/ZBXNEXT-7852-6.4-D to release/6.4

* commit '8412514c72d73c9e2ca6f6162307a9952f175bb5':
  [ZBXNEXT-7852] Updated "Passive and active agent checks"
  [ZBXNEXT-7852] Updated "Upgrade notes", "What's new"
  [ZBXNEXT-7852] Updates to character encoding & IDs
  [ZBXNEXT-7852] Updates to "Upgrade notes"
  [ZBXNEXT-7852] Updates to JSON protocols
  [ZBXNEXT-7852] Updates to JSON protocols
  [ZBXNEXT-7852] Corrections to various sections
  [ZBXNEXT-7852] Updates to JSON protocols
  [ZBXNEXT-7852] Updated "User macros"
  [ZBXNEXT-7852] Updated "Upgrade notes", "What's new"
  [ZBXNEXT-7852] Updates for RefreshActiveChecks