documentation

Pull request #1297: feature/ZBXNEXT-8421-7.0-D: Host dashboards tabs (documented new feature, restructured pages, updated images).

Merge in WEB/documentation from feature/ZBXNEXT-8421-7.0-D to release/7.0

* commit '2b334f49928a7a11cc98956cae576d2fee20bb3a':
  [ZBXNEXT-8421] Updated host dashboards images (in Quick reference guides)
  [ZBXNEXT-8421] Refined wording
  [ZBXNEXT-8421] Host dashboards tabs (documented new feature, restructured pages, updated images)