More LTN feature requests

[dabreegster]

• Allow edits on the perimeter road? (The "proper" fix is to extend the boundary until the perimeter is a main road, and never a residential street that just happens to back up to the edge of a map)
• Add a modal filter for school streets / time-dependent closures (just a new icon, no semantic difference)
• Be able to draw traffic calming / speed tables / 20mph zones (on any road, including perimeter). Not sure how to visually represent yet. Probably per road segment. And probably allow on perimeter roads too

[dabreegster]

Closing for now, because the first idea wasn't necessary after extending the Stapleford boundary. It's still an interesting idea, but I think it's not ideal.