Added "Accept-Ranges" header when serving arbitrary data.

Allows for video seeking when using URL playback, even though the Range header isn't implemented yet. This could be heavily optimized by adding full support of the Range/Content-Range headers, however this is still a big step forward as it allows for (inefficient) seeking.

src/main/java/org/qortal/api/resource/ArbitraryResource.java

@@ -1341,6 +1341,7 @@ public class ArbitraryResource {
 				data = Base64.encode(data);
 			}
 
+			response.addHeader("Accept-Ranges", "bytes");
 			response.setContentType(context.getMimeType(path.toString()));
 			response.setContentLength(data.length);
 			response.getOutputStream().write(data);