Edit screen UI for post formats: a first run for functionality.

* Adds a very basic tabbed interface for selecting a post format (requires JS).
* Extra fields, which are post meta, are shown/hidden based on the selected format.
* Introduce a helper function for retrieving formats-specific metadata: `get_post_format_meta()`.
* Image selection uses the media modal, although without filtering or from URL support at the moment.

props rachelbaker, wonderboymusic, aaroncampbell, helen. see #19570.


git-svn-id: https://develop.svn.wordpress.org/trunk@23449 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/post.php

@@ -1950,6 +1950,30 @@ function get_post_custom_values( $key = '', $post_id = 0 ) {
 	return isset($custom[$key]) ? $custom[$key] : null;
 }
 
+/**
+ * Retrieve post format metadata for a post
+ *
+ * @since 3.6.0
+ *
+ * @param int $post_id
+ * @return null
+ */
+function get_post_format_meta( $post_id = 0 ) {
+	$values = array(
+		'quote'        => '',
+		'quote_source' => '',
+		'image'        => '',
+		'url'          => '',
+		'gallery'      => '',
+		'media'        => '',
+	);
+
+	foreach ( $values as $key => $value )
+		$values[$key] = get_post_meta( $post_id, '_wp_format_' . $key, true );
+
+	return $values;
+}
+
 /**
  * Check if post is sticky.
  *