documentation

Pull request #2549: Feature/DEV-2543 7.3 D v2

Merge in WEB/documentation from feature/DEV-2543-7.3-D-v2 to release/7.4

* commit '35285b34b62d761876f959549b6d3f1b633be8f3':
  DEV-2543 updated a comment.
  DEV-2543 updated comments.
  DEV-2543 changed privacy protocol.
  DEV-2543 added info on installing custom MIBs.
  DEV-2543 updated screenshot, addes OID names translation section, fixed command example.
  DEV-2543 command example generalization.
  DEV-2543 added screenshot, command examples generalization.
  DEV-2543 guide improvements.
  DEV-2543 added info for SNMPv3 and troubleshooting section.