Garden editor for the rest of the lot (v2)

The house takes any part of a lot (#173, docs/building-editor.md § 1.1); the rest is the yard. A second editor for it: fences and gates, paths, garden beds and crops, trees and bushes, wells, benches and the other garden props of the catalog (#104), with the same plan, cost line and instant raise as the building editor. v2: until then the yard keeps the town's ground and dressing.