Options for YouTube player

Add a config option to change player style for dark.

Example:

// create timeline
          timeline = createStoryJS({
            type: 'timeline',
            embed_id: 'timeline',
            debug: false,
            youtubeTheme: "dark",
            source: { ... }
          });

source/js/Core/Media/VMM.ExternalAPI.js

@@ -1435,9 +1435,9 @@ if(typeof VMM != 'undefined' && typeof VMM.ExternalAPI == 'undefined') {
 					width: 					'640',
 					playerVars: {
 						enablejsapi: 1,
-						color: 				'white',
+						color: ("dark" == VMM.master_config.Timeline.youtubeTheme) ? "black" : "white",
 						showinfo: 0,
-						theme:				'light',
+						theme: ("undefined" !== VMM.master_config.Timeline.youtubeTheme) ? VMM.master_config.Timeline.youtubeTheme : "light",
 						start: m.start,
 						rel: 0
 					},