Administration: Improve user experience and clarify when in recovery mode.

This changeset introduces several changes around usability when recovery mode is active:

* Display a notice in the admin clarifying that the user is in recovery mode.
* Use a highlight color for the admin bar link to exit recovery mode.
* Exit recovery mode automatically when logging out.
* Include a recovery mode indicator in the title tag.

Props aandrewdixon, azaozz, dhanukanuwan, flixos90, henrywright, karmatosed, mapk, melchoyce, spacedmonkey, TimothyBlynJacobs, tinkerbelly.
See #46608.

Built from https://develop.svn.wordpress.org/trunk@45117


git-svn-id: http://core.svn.wordpress.org/trunk@44926 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/admin-header.php

@@ -52,6 +52,11 @@ if ( $admin_title == $title ) {
 	$admin_title = sprintf( __( '%1$s ‹ %2$s — WordPress' ), $title, $admin_title );
 }
 
+if ( wp_is_recovery_mode() ) {
+	/* translators: %s: Admin screen title. */
+	$admin_title = sprintf( __( '%s — Recovery Mode' ), $admin_title );
+}
+
 /**
  * Filters the title tag content for an admin page.
  *