Start rearranging the docs for a utilities update

— Rename display docs page
— Move print display utils to display utils page
— Drop remaining of responsive utils page as it's being replaced with display utils
— Update nav to reflect changes

docs/_data/nav.yml

@@ -15,7 +15,7 @@
     - title: Overview
     - title: Grid
     - title: Media object
-    - title: Responsive utilities
+    - title: Utilities for layout
 
 - title: Content
   pages:
@@ -56,8 +56,8 @@
     - title: Clearfix
     - title: Close icon
     - title: Colors
+    - title: Display
     - title: Flexbox
-    - title: Display property
     - title: Image replacement
     - title: Invisible content
     - title: Position