Update handling added

• Installed and remote versions are now being compared
  • User will be prompted should a newer version exist and 'selected_version' in 'config.dat' not be set to 'latest'
• Installed and 'selected_version' versions are new being compared
  • User will be prompted should 'selected_version' not exist or not be found, notifying them of the discrepancy
  • User will be prompted should 'selected_version' be found and asked whether they want to down-/upgrade
• Windows support not guaranteed, may need to be adjusted and is thus only a minor change as revisions are likely to follow