Release v6.15.0

• (foxriver76) harmonized the links to adapter documentation (and fallback to english if no explicit doc for sys language provided)'
  '* (bluefox) added possibility to delete whole adapter from instance tab if only one instance left'
  '* (foxriver76) new dialog for notifications introduced for non-system notifications (system notifications are still on hosts tab)'
  '* (foxriver76) the new licenseInformation icon now changes color correctly with the theme