Resolves #373 - Adds support for Tuner frequency error PPM monitoring

and auto-correction for R820T tuners.

-Updated TunerModel and TunerViewPanel to add 2 new columns to
display the current tuner's PPM setting and (when available) the
measured frequency error averaged over 5 second intervals provided by
certain decoders (e.g. P25 C4FM and LSM).  Frequency error value from
P25 decoders is provided from the Costas Loop PLL once 2 or more P25
message sync events have been observed in a short period.
-Updated R820T tuner to auto-correct PPM when measured frequency error
exceeds the +/- 0.4PPM threshold for a period of 30 seconds or more.
Feature can be enabled/disabled by user in the tuner editor panel.

Resolved several issues with P25 C4FM/LSM decoders that was impacting
performance related to channel misalignment from tuner PPM offsets.

src/main/java/io/github/dsheirer/dsp/fsk/LTRDecoder.java

@@ -134,6 +134,12 @@ public class LTRDecoder implements Listener<ReusableBuffer>, ISyncDetectListener
         mSynchronizationMonitor.syncDetected();
     }
 
+    @Override
+    public void syncLost()
+    {
+        //no-op
+    }
+
     /**
      * Processes the buffer samples by converting all samples to boolean values reflecting if the sample value is
      * greater than zero (or not).  Average symbol timing offset is calculated for the full buffer and the offset is

src/main/java/io/github/dsheirer/dsp/fsk/SynchronizationMonitor.java

@@ -30,13 +30,13 @@ import org.slf4j.LoggerFactory;
  *
  * Synchronization States:
  *
- *  -COARSE - default state.  demoted from MEDIUM after one message period with no sync detection.
+ * -COARSE - default state.  demoted from MEDIUM after one message period with no sync detection.
  *
- *  -MEDIUM - promoted from COARSE when one sync detection occurs after two message periods, or demoted from FINE
- *            after two message periods with no sync detections.
+ * -MEDIUM - promoted from COARSE when one sync detection occurs after two message periods, or demoted from FINE
+ * after two message periods with no sync detections.
  *
- *  -FINE   - promoted from MEDIUM after two or more consecutive sync detections within the preceding two or more
- *            message periods.
+ * -FINE   - promoted from MEDIUM after two or more consecutive sync detections within the preceding two or more
+ * message periods.
  */
 public class SynchronizationMonitor implements ISyncDetectListener
 {
@@ -50,6 +50,7 @@ public class SynchronizationMonitor implements ISyncDetectListener
 
     /**
      * Constructs the synchronization monitor for the specified message symbol length.
+     *
      * @param messageLength in symbols.
      */
     public SynchronizationMonitor(int messageLength)
@@ -127,6 +128,12 @@ public class SynchronizationMonitor implements ISyncDetectListener
         updateSyncState();
     }
 
+    @Override
+    public void syncLost()
+    {
+        //no-op
+    }
+
     /**
      * Increments the symbol count for each decoded symbol.
      */