file: format symbol.jade, fix #2038

vispa/extensions/file/static/html/symbol.jade

 .file-view-symbol.file-list.icon-tiny
-    .file-node(draggable="true", data-bind="data")
-        p.file-selection-p
-            label.file-selection-box
-                input(type="checkbox").file-selection-checkbox
-                span
-            p.glyphicon.glyphicon-cog.file-properties
-        //- p.symbol-icon-p
-        .symbol-icon-p
-            span(data-bind="icon")
-        p(data-bind="name").symbol-name
+  .file-node(draggable="true", data-bind="data")
+    p.file-selection-p
+      label.file-selection-box
+        input(type="checkbox").file-selection-checkbox
+        span
+      p.glyphicon.glyphicon-cog.file-properties
+    //- p.symbol-icon-p
+    .symbol-icon-p
+      span(data-bind="icon")
+    p(data-bind="name").symbol-name