add upgrade path for landuse=churchyard

closes #4

data/deprecated.json

@@ -818,6 +818,10 @@
     "old": {"landuse": "basin"},
     "replace": {"natural": "water", "water": "basin"}
   },
+  {
+    "old": {"landuse": "churchyard"},
+    "replace": {"landuse": "religious"}
+  },
   {
     "old": {"landuse": "conservation"},
     "replace": {"boundary": "protected_area"}