Add ability to delete maps

[huderlem]

This one might be a bit tricky because there are many places in the decompilation projects that would be affected. And what if another map has a warp that points to the deleted map? Lots of things to consider.

@ProjectRevoTPP

ProjectRevoTPP commented on Feb 19 from the Discord:

in a better map editor there might be an option to "Delete Anyway" but default is no that way someone can do quick work of a bunch of maps by deleting anyway so they dont need to hand delete a bunch for each like if someone is redoing a region they want the whole region deleted it would be really slow to do one at a time so i think a "Delete anyway" option would work, but it should be not easy to misclick and a confirmation Yes/No after with no default highlighted, of course

(originally from https://github.com/yenatch/pretmap/issues/9)

[huderlem]

Probably shouldn't be a Porymap feature, due to lots of accompanying deletions that would need to be done outside the context of Porymap.