documentation

Pull request #1566: feature/ZBXNEXT-8721-7.0-D. Added net.dns.get item.

Merge in WEB/documentation from feature/ZBXNEXT-8721-7.0-D to release/7.0

* commit '604fbd4d2f4473f0ca84bcb126c00f1883d7eaf0':
  [ZBXNEXT-8721] Refined wording
  [ZBXNEXT-8721] Updated examples
  [ZBXNEXT-8721] Updated examples
  [ZBXNEXT-8721] Updated wording and formatting
  [ZBXNEXT-8721] Fixed blockIDs
  [ZBXNEXT-8721] Refined item description; added link to related Appendix page
  [ZBXNEXT-8721] New page on return values for net.dns.get
  [ZBXNEXT-8721] Preparation for new page on return values for net.dns.get
  [ZBXNEXT-8721] Escaping unnecessary italics
  [ZBXNEXT-8721] net.dns.* items require `name` parameter
  [ZBXNEXT-8721] Refined wording for consistency
  [ZBXNEXT-8721] Refined wording for `flags` parameter possible values
  [ZBXNEXT-8721] Added net.dns.get item `type` parameter default value
  [ZBXNEXT-8721] Added net.dns.perf to items listed for Windows permissions
  [ZBXNEXT-8721] Added net.dns.get item