This adds a map for Cinnabar Volcano's floors in the run-up to Moltres. I used a S.S. Anne style compression technique here, having 4 floors on a decently sized map that are just far enough apart for a player to never actually see them. This maintains their suspension of disbelief while giving us way more space to work with. I want to compress a lot of RBY maps like this if push comes to shove - there's a lot of places where this is possible.
In the interests of compression, I started using the Agatha bank again, as I removed a lot of maps from there when making bank 22. There's some space for maps.
Also I made 3 more blocks for cavern which caused it to overflow the bank it was in - fixed that by swapping with PreGym, which is probably much smaller.
Cinnabar Volcano hasn't been changed yet in the interest of Martha finishing that bit up.
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
