Fixes #1519

Please provide some details about this pull request:

• Set DNS server globaly in settings
• Impove DNS server resolving after connection change (re-set dns server)
• [DEPRECATED] IP scanner - dns server settings

ToDo:

• Implement everywhere...
• Cleanup IP scanner
• Reset DNS servers when network change

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• The code or resource is compatible with the GNU General Public License v3.0.