add preset for landuse=salt_pond (closes #258)

data/presets/landuse/salt_pond.json

@@ -0,0 +1,25 @@
+{
+    "icon": "maki-triangle-stroked",
+    "fields": [
+        "name",
+        "operator"
+    ],
+    "geometry": [
+        "area"
+    ],
+    "tags": {
+        "landuse": "salt_pond"
+    },
+    "terms": [
+        "evapoation",
+        "saline",
+        "salt",
+        "salt works",
+        "salt pan"
+    ],
+    "aliases": [
+        "Salt Pond",
+        "Saltern"
+    ],
+    "name": "Salt Evaporation Pond"
+}