documentation

Pull request #288: Feature/ZBX-19369 6.0 D

Merge in WEB/documentation from feature/ZBX-19369-6.0-D to release/6.0

* commit 'd5b01360c6c3e6353bb9cebd3c516217f6bd5baf':
  remove wrong edit
  [ZBX-21208] security best practices update, authentication
  [ZBX-21208] security best practices update
  [ZBX-19369] agent2 protocol page
  [ZBX-19369] agent2 protocol page
  [ZBX-19369] adding agent 2 protocol page