refactoring of pane => split, "pane" keeps its old meaning (left-pane, center-pane, right-pane)

src/public/app/widgets/containers/left_pane_container.js

@@ -0,0 +1,21 @@
+import options from "../../services/options.js";
+import FlexContainer from "./flex_container.js";
+
+export default class LeftPaneContainer extends FlexContainer {
+    constructor() {
+        super('column');
+
+        this.id('left-pane');
+        this.css('height', '100%');
+    }
+
+    isEnabled() {
+        return super.isEnabled() && options.is( 'leftPaneVisible');
+    }
+
+    entitiesReloadedEvent({loadResults}) {
+        if (loadResults.isOptionReloaded("leftPaneVisible")) {
+            this.toggleInt(this.isEnabled());
+        }
+    }
+}