documentation

Pull request #2535: feature/DEV-4228-7.0-D-v2. improved Windows agent installation instructions and agent/agent2 general installation instructions; added agent2 loadable plugin installation instructions.

Merge in WEB/documentation from feature/DEV-4228-7.0-D-v2 to release/7.0

* commit '7c90428951ebfe61e7ba698312c600a7a79c0d67':
  [DEV-4228] fixed links; updated ADDEFAULT, ADDLOCAL parameters
  [DEV-4228] fixed formatting shortcomings
  [DEV-4228] updated ADDEFAULT, ADDLOCAL, TLS-related parameters; converted Ember+ plugin note into regular text
  [DEV-4228] added NONMSICONFNAME parameter
  [DEV-4228] improved agent/agent2 general installation instructions
  [ZBX-26086] added agent2 loadable plugin installation instructions
  [DEV-4228] improved Windows agent installation instructions