#652 USB Tuner Error Handling Enhancements (#653)

-Separates USB timeout event processing to a dedicated thread
-Updates USB transfer buffer processor to better detect errors and auto-restart on error (max 3 times)
-Updates Tuner to add an error state and SourceManager to not select tuners with an error state
-Updates ChannelProcessingManager to auto-shutdown channels sourced from tuners set with error state
-Improves logging of USB related errors.

src/main/java/io/github/dsheirer/dsp/filter/channelizer/PolyphaseChannelManager.java

@@ -1,7 +1,7 @@
 /*
  *
  *  * ******************************************************************************
- *  * Copyright (C) 2014-2019 Dennis Sheirer
+ *  * Copyright (C) 2014-2020 Dennis Sheirer
  *  *
  *  * This program is free software: you can redistribute it and/or modify
  *  * it under the terms of the GNU General Public License as published by
@@ -126,6 +126,18 @@ public class PolyphaseChannelManager implements ISourceEventProcessor
         this(tunerController, tunerController.getFrequency(), tunerController.getSampleRate());
     }
 
+    /**
+     * Signals to all provisioned tuner channel sources that the source complex buffer provider has an error and can
+     * no longer provide channels, so that the tuner channel source can notify the consumer of the error state.
+     */
+    public void setErrorMessage(String errorMessage)
+    {
+        for(TunerChannelSource tunerChannelSource: mChannelSources)
+        {
+            tunerChannelSource.setError(errorMessage);
+        }
+    }
+
     /**
      * Current channel sample rate which is (2 * channel bandwidth).
      */