Proper heading for admin screens.

First step towards restoring a good heading structure in wp-admin.
The previous `<h1>` contained the site title and a link to the front page and was removed with the toolbar refactoring in 3.2.

Props joedolson, afercia.
Fixes #31650.


Built from https://develop.svn.wordpress.org/trunk@32974


git-svn-id: http://core.svn.wordpress.org/trunk@32945 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/common-rtl.css

@@ -328,6 +328,7 @@ h1 {
 	margin: .67em 0;
 }
 
+.wrap > h1,
 h2 {
 	color: #23282d;
 	font-size: 1.5em;
@@ -564,12 +565,14 @@ code {
 	color: #00a0d2;
 }
 
+.wrap h1,
 .wrap h2,
 .subtitle {
 	font-weight: normal;
 	margin: 0;
 }
 
+.wrap h1,
 .wrap h2 {
 	font-size: 23px;
 	font-weight: 400;