Add core support for Playlists and Video Playlists.

* Playlists operate like galleries in the admin. 
* Provide default UI and JS support in themes using MediaElement and Backbone. 
* The shortcodes are clickable, editable, and configurable using the media modal. 
* Playlists support images for each item, whether or not the current theme supports images for `attachment:audio` and `attachment:video`
* Playlists respond to `$content_width` and resize videos accordingly.
* All playlist data is included inline, using a script tag with `type="application/json"`, allowing anyone to unenqueue the WP playlist JS and roll their own.
* Playlist styles are minimal and work out of the box in the last 5 default themes. They inherit and adapt to the current theme's font styles, and their rules are easily overrideable.

See #26631.



git-svn-id: https://develop.svn.wordpress.org/trunk@27239 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/media-template.php

@@ -411,6 +411,47 @@ function wp_print_media_templates() {
 		</label>
 	</script>
 
+	<script type="text/html" id="tmpl-playlist-settings">
+		<h3><?php _e('Playlist Settings'); ?></h3>
+
+		<label class="setting">
+			<span><?php _e( 'Random Order' ); ?></span>
+			<input type="checkbox" data-setting="_orderbyRandom" />
+		</label>
+
+		<label class="setting">
+			<span><?php _e('Style'); ?></span>
+			<select class="style" data-setting="style">
+				<option value="light">
+					<?php esc_attr_e('Light'); ?>
+				</option>
+				<option value="dark">
+					<?php esc_attr_e('Dark'); ?>
+				</option>
+			</select>
+		</label>
+
+		<label class="setting">
+			<span><?php _e( 'Show Tracklist' ); ?></span>
+			<input type="checkbox" data-setting="_tracklist" />
+		</label>
+
+		<label class="setting">
+			<span><?php _e( 'Show Track Numbers' ); ?></span>
+			<input type="checkbox" data-setting="_tracknumbers" />
+		</label>
+
+		<label class="setting">
+			<span><?php _e( 'Show Artist Name in Tracklist' ); ?></span>
+			<input type="checkbox" data-setting="_artists" />
+		</label>
+
+		<label class="setting">
+			<span><?php _e( 'Show Images' ); ?></span>
+			<input type="checkbox" data-setting="_images" />
+		</label>
+	</script>
+
 	<script type="text/html" id="tmpl-embed-link-settings">
 		<label class="setting">
 			<span><?php _e('Title'); ?></span>