Underwater Tunnel is a new area that links Route 25 to Route 10, basically just being a straight tunnel needing Surf to traverse.
Also given Seafoam Islands and Lorelei's room an unused palette that gives it a more icy feel
* Update sign to bg_event #289
* Rename warp to warp_event
* Replace object to object_event
* Move warp macro parameter from warp x, y, id, map to warp_event x, y, map, id