documentation

Pull request #1787: feature/ZBXNEXT-8686-7.0-D-API. Added Item navigator widget (API).

Merge in WEB/documentation from feature/ZBXNEXT-8686-7.0-D-API to release/7.0

* commit '610bc6b7dcf386bcc042d19f9525db7747222ebe':
  [ZBXNEXT-8686] renamed "host/item pattern" to "host/item patterns" (API)
  [ZBXNEXT-8686] fixed show_lines parameter support
  [ZBXNEXT-8686] added Item navigator widget (API)
  [ZBXNEXT-8686] copied host_navigator.md as a template for item_navigator.md (API)