Hides dispay of grandchildren

Display of grandchildren links in the navigation is now delayed until their parent is selected.

To test, select the `Grandchildren test` node. Only the direct children should appear. Selecting one of them then shows its children.

docs/grandchildren-test/buttons.md

@@ -0,0 +1,11 @@
+---
+layout: default
+title: Buttons
+parent: Grandchildren test
+has_children: true
+---
+
+Buttons
+----
+
+Child of [Grandchildren test](..)

docs/grandchildren-test/buttons/grandchild.md

@@ -0,0 +1,9 @@
+---
+layout: default
+title: Buttons Child Page
+parent: Buttons
+grand_parent: Grandchildren test
+---
+
+Buttons Child Page
+----

docs/grandchildren-test/index.md

@@ -0,0 +1,12 @@
+---
+layout: default
+title: Grandchildren test
+has_children: true
+nav_order: 8
+---
+
+Grandchildren test
+==================
+
+Has a child [Buttons](buttons)
+and a grandchild [Child of Buttons](buttons/grandchild)

docs/grandchildren-test/labels.md

@@ -0,0 +1,11 @@
+---
+layout: default
+title: Labels
+parent: Grandchildren test
+has_children: true
+---
+
+Labels
+----
+
+Child of Grandchildren test

docs/grandchildren-test/labels/label-grandchild.md

@@ -0,0 +1,9 @@
+---
+layout: default
+title: Labels Child Page
+parent: Labels
+grand_parent: Grandchildren test
+---
+
+Labels Child Page
+----