NMS-6634: Documentation DnsMonitor

- Created complete parameter description
- Created example testing DNS lookup for A record against www.google.com
NMS-6634: Documentation DnsMonitor

- Review suggestion to emphasize the monitor sends a DNS request for "A" record types only.
NMS-6634 Documentation DnsMonitor

- Created reference in DNSResolutionMonitor to be linkable
- Added tip when using DNSResolutionMonitor with link
- Fix: Added DnsMonitor in main doc
Merge pull request #71 from indigo423/NMS-6634-docs-DnsMonitor

NMS-6634: Documentation DnsMonitor