Use Heightgraph in lieu of Elevation (part V)

- fix the grade calculation
- don't show the grade labels, as they are all over (should be normalized)
- fix the display issues by overridding the heightgraph CSS

css/style.css

@@ -743,3 +743,15 @@ table.dataTable.display tbody tr:hover.selected {
     so we ignore pointer events in this situation to avoid that*/
     pointer-events: none;
 }
+
+/*
+ * Heightgraph customizations;
+ * since the gradient types are empty, hide the legend as it's useless;
+ * since there's only the gradient layer, hide the layer selector.
+ */
+.legend-hover {
+    display: none;
+}
+#selectionText {
+    display: none;
+}