Move xml gen. into view for (old) nodes, ways, relations, map

app/views/api/old_nodes/_old_node.xml.builder

@@ -0,0 +1,24 @@
+attrs = {
+  "id" => old_node.node_id,
+  "visible" => old_node.visible,
+  "version" => old_node.version,
+  "changeset" => old_node.changeset_id,
+  "timestamp" => old_node.timestamp.xmlschema,
+  "user" => old_node.changeset.user.display_name,
+  "uid" => old_node.changeset.user_id
+}
+
+if old_node.visible
+  attrs["lat"] = old_node.lat
+  attrs["lon"] = old_node.lon
+end
+
+if old_node.tags.empty?
+  xml.node(attrs)
+else
+  xml.node(attrs) do |nd|
+    old_node.tags.each do |k, v|
+      nd.tag(:k => k, :v => v)
+    end
+  end
+end