Extend location sheet for SI

[ben]

There are a few things in Sundered Isles that we can use the location sheet for.

• Extend the "region" dropdown to include SI values (if SI is enabled)
• Extend the "location type" dropdown to include island and settlement (if SI is enabled)
• Hide the subtype for islands, show shore/inland/waterside
• Oracle sets for islands and settlements
• Sidebar tools
  • Add buttons for islands and settlements
  • Default icons for islands and settlements
• Update CHANGELOG.md