Add script to extract traditional Eclipse icons for backup/restore

[vogella]

ExtractTraditionalIcons.java reads icon-mapping.json and extracts every referenced icon from an existing Eclipse installation (JAR and directory plugins) into iconpacks/eclipse-traditional-icons/, preserving the plugin-relative path structure. It also writes icon-restore-mapping.json so a restore script knows which dual-tone icon replaced each original.

[vogella]

@Michael5601 this script allows to extract the existing svg icons from an Eclipse installation and create a new folder with the old icons and mapping. This way we could change an installation back to the old icons.

[Michael5601]

Thank you for your work @vogella. What is the idea behind this? Shall this program revert the changes your other bash script does for testing purposes?

Just so our perspectives are clear: The new dual tone icon pack will probably never fully replace the default eclipse icons as too many software products are based on these icons and also probably all marketplace plugins that introduce new icons are oriented on the old icons.
The new dual tone icon pack can only be used once we have a technical solution for changing icons in the Eclipse Settings so the user can switch between icon packs dynamically. We have not yet started to develop this solution. So currently we don't "lose" the default icons and thus need no way to restore them afaik.