Release version 16.0.0

Added
* standalone web page to generate and download diagnostics
* standalone web page to export, remove or rollback system snapshots
* S.M.A.R.T. drive diagnostics as part of filesystems module

Fixed
* follow symlink for `dump_file` text file detection
* invalid locale `nb` renamed to the correct `nb_NO`

Changed
* removed old Turris specific firewall diagnostics that are no longer
  valid