Use "building_area" field for all amenities

This field will preserve a building=yes tag when
switching to from the Building preset.

Refs #1408.

data/presets/presets.json

@@ -551,7 +551,7 @@
             "amenity": "marketplace"
         },
         "fields": [
-            "building"
+            "building_area"
         ],
         "name": "Marketplace"
     },
@@ -599,7 +599,7 @@
         "fields": [
             "religion",
             "denomination",
-            "building",
+            "building_area",
             "address"
         ],
         "geometry": [
@@ -881,7 +881,7 @@
         "icon": "school",
         "fields": [
             "operator",
-            "building",
+            "building_area",
             "address"
         ],
         "geometry": [
@@ -962,7 +962,7 @@
     "amenity/toilets": {
         "fields": [
             "operator",
-            "building"
+            "building_area"
         ],
         "geometry": [
             "point",

data/presets/presets/amenity/marketplace.json

@@ -8,7 +8,7 @@
         "amenity": "marketplace"
     },
     "fields": [
-        "building"
+        "building_area"
     ],
     "name": "Marketplace"
 }

data/presets/presets/amenity/place_of_worship.json

@@ -3,7 +3,7 @@
     "fields": [
         "religion",
         "denomination",
-        "building",
+        "building_area",
         "address"
     ],
     "geometry": [

data/presets/presets/amenity/school.json

@@ -2,7 +2,7 @@
     "icon": "school",
     "fields": [
         "operator",
-        "building",
+        "building_area",
         "address"
     ],
     "geometry": [

data/presets/presets/amenity/toilets.json

@@ -1,7 +1,7 @@
 {
     "fields": [
         "operator",
-        "building"
+        "building_area"
     ],
     "geometry": [
         "point",