download controller: add API so other objects can queue a download

AspenProject/VLCDownloadViewController.h

@@ -24,4 +24,6 @@
 
 - (IBAction)downloadAction:(id)sender;
 - (IBAction)cancelDownload:(id)sender;
+
+- (void)addURLToDownloadList:(NSURL *)aURL;
 @end

AspenProject/VLCDownloadViewController.m

@@ -241,4 +241,11 @@
     }
 }
 
+#pragma mark - communication with other VLC objects
+- (void)addURLToDownloadList:(NSURL *)aURL
+{
+    [_currentDownloads addObject:aURL];
+    [self _triggerNextDownload];
+}
+
 @end