only apply layer=1 on newly creted roofs; improve fields for roof preset

* closes #1432 by changing the `layer=1` tag from an `addTags` tag to the default value of the `layer` field
* some of the fields for "regular" buildings don't make sense for "roof-only" features

Author: tyrasd

data/fields/layer_1.json

@@ -0,0 +1,7 @@
+{
+    "key": "layer",
+    "type": "number",
+    "label": "{layer}",
+    "placeholder": "0",
+    "default": "1"
+}

data/presets/building/roof.json

@@ -1,19 +1,30 @@
 {
     "icon": "maki-shelter",
     "fields": [
-        "{building}",
-        "layer"
+        "building",
+        "height",
+        "layer_1"
+    ],
+    "moreFields": [
+        "address",
+        "architect",
+        "building/colour",
+        "building/levels",
+        "building/levels/underground",
+        "building/material",
+        "building/prefabricated",
+        "ele",
+        "gnis/feature_id-US",
+        "not/name",
+        "operator",
+        "roof/colour"
     ],
     "geometry": [
         "area"
     ],
     "tags": {
         "building": "roof"
     },
-    "addTags": {
-        "building": "roof",
-        "layer": "1"
-    },
     "matchScore": 0.5,
     "name": "Roof"
 }

data/presets/power/generator/method/photovoltaic/building/roof.json

@@ -1,7 +1,8 @@
 {
     "icon": "fas-solar-panel",
     "fields": [
-        "{power/generator/method/photovoltaic}"
+        "{power/generator/method/photovoltaic}",
+        "layer_1"
     ],
     "moreFields": [
         "{power/generator}"
@@ -22,8 +23,7 @@
         "generator:method": "photovoltaic",
         "generator:type": "solar_photovoltaic_panel",
         "generator:output:electricity": "*",
-        "building": "roof",
-        "layer": "1"
+        "building": "roof"
     },
     "reference": {
         "key": "generator:method",